I also commuted in those very noisy and very poorly maintained buses in Boston (the "new" ones). And my commute in Tokyo included walking on busy streets, subways and (less noisy) buses.
First off, I would like to think that the technological development of earbuds and headphones is still in its infancy; that means sound reproduction is not all that great yet. I am a bit reluctant to recommend any products but you asked so I outline two options I consider enjoyable, well-engineered and cheap:
I was looking for a decent balance among: 0) sound "quality" and 1) sound insulation of outside noise and 2) a bass bump that helps compensate for outside transportation noise and 3) decent durability and 4) low "microphonics" so the cables are not irritatingly noisy when you walk or just move around the desk.
==> My best $20 commuting earbud is the sennheiser cx-150. You can still find it online for sale in the US for around $20-30. The CX-213 looks identical but published "specs" may be slightly different (I suspect they may be just relabeled and priced up a few dollars). The CX1.00 looks to be the replacement and both physical design and characteristics have changed a bit. The cx-150 has virtually no irritating "microphonics." After 6 years of abuse, my cx-150 are still working perfectly; however the 1/8" jack became unglued from the rubber housing so is a bit sloppy when removing from the phone jack and will die someday. I tried hot glue but that failed quickly. I also lost the original rubber tips and replaced them with foamy "comply" tips; see below. OEM replacement rubber tips are available for about $25 (!)
==> My favorite commuting earbud is the JVC HA-FX850. The bass bump can sometimes drive you bonkers at home but I am 100% sure the JVC team was commuting in Tokyo during the tuning phase. It is about $250 at Amazon. I don't know if it is available in brick-and-mortar stores in the US. Cable has some irritating microphonics and is pretty short, but the included alligator clip connected to my shirt collar eliminate all microphonics for me. This is the one piece of audio equipment I really enjoy using. But your cat may also enjoy eating at the exotic wood frame, soft rubber cable, and leather storage box. Very robust industrial engineering and cable is easy to replace. Don't be distracted by similar JVC models.
FYI -a couple of commuter comments with respect to "outside sound isolation" and "microphonics" (irritating noise cables seem to make when you are walking or just move at desk). I guess some types of "cable materials" are noisy and some types of "gaskets" are noisy; the trick is getting a good combination of the two.
I think earbuds can have a few basic types of "gaskets" that connect to your ears:
a) hard plastic is good for walking or jogging as it doesn't seem to communicate irritating cable sound. It provides lousy "outside sound isolation" and can be irritating in windy conditions. The sound can be quite airy but also lack bass. Typical for those free white i-phone headphones but also used in some high-quality earbuds.
b) Thick foamy tips like the "Comply" brand. They do a good job of "outside sound isolation" but provide a big bass bump and kill airyness (however you define that). Can be quite microphonic. If your bus is really noisy, this might be a good idea.
c) Soft rubber gaskets are a compromise between the hard plastic and thick foamy and generally best solution combining commuter & audio goals for me.
The Sennhiesers provide a few sizes of the c) soft rubber gaskets. The JVC comes with both b) thick foamy compy-type tips and a few sizes of the c) soft rubber gaskets.
Also, there are some of those heavy-metal ear monitors (some are custom made for your ears) which can provide poor to excellent noise isolation. They often have several drivers and what we can call primitive crossovers. Never heard one that sounded right, but maybe they work better with a custom ear mold.
Finally, there is also a case for using noise-reduction headphones, but they are big and sound quality is generally a second priority. The noise-reduction earbuds are worthless as the noise reduction technology works better at low frequencies that earbuds just don't excel at. On-ear noise reduction headphones rest on your ears and those hurt after time. Over-ear noise reduction headphones are the most effective and most comfortable in my experience. Like or hate Bose, the new Bose noise cancellation phones have the best noise-cancellation algorithm by a wide margin. The previous generation is very close and a lot cheaper. But for very noisy environments, the Bose provides a very good combination of noise cancellation, sound quality, comfort and price. For quiet environments, look elsewhere.
Ha! Maybe I can help. I lived in Tokyo for a few years and tried to find the "perfect" commuting earbuds. Tokyo's "Best Buy" type electronics stores are huge and typically stock 100s of different models. There are also two large headphone specialty stores. So it was the best place in the world for some sampling. In Boston I think the little store in the Harvard Square Garage and the little store that fixed your Yamaha B2 stock a few (half-dozen) earbuds, but you need to check before traveling.