Can you get a wheeled carrier? This specific one is "up to 22 pounds" ELEGX Expandable Pet Rolling Carrier Backpack with Detachable Wheels,（13.6" Lx10.4 Wx19.1 H）, Plenty of Room, Collapsible, Breathable, for Medium Dog & Cat Car Seat Travel and Outdoor Hiking https://www.amazon.com/dp/B092D6MS2V/ref=cm_sw_r_apan_glt_fabc_WD657BANTAVRHG76SSS0?_encoding=UTF8&psc=1

Something I would consider is if your dog can reasonably handle a bus, they can often be scary experiences for dogs who have not been properly prepped for them. Then there is the fact that there is always the risk of something happening to the carrier while you ride since generally there is not space to put them somewhere out of the way. A service or guide dog can often be tucked into a semi-awkward position in the pursuit of a more safe ride because their body is more flexible than a carrier which outside of a few rare situations will have to be in the way of foot traffic. Ultimately I would advise against transporting an animal in a carrier on a bus unless you can insure that they can ride on your lap or some other similar situation where you can protect them from the minimally predictable nature of the bus.

I'm going to be honest, it's a friggan pain in the ass even with a retired service dog, especially one that is sick. Had a service dog that passed away last year. Damn vet was closed when I discovered him, and it is by the grace of God that we protested and cried at the entrance of the BMV to allow our daughter to get her first driver's license during the main pandemic when agencies were going by appointment only. Ended up having to take him to my father in law's land to dig and bury him. Nearest place was really far away and expensive. Have a doberman shepherd that's three and was definitely a pain once I moved away from the walking trail that practically led to the door step of a vet. Found a local car service that did medicab and private taxi service for emergencies eventually. A He kind of disappeared though. I found that if you can find private taxi companies that they are willing to help out if the understand the situation, and you can almost buy yourself out of anything when you're blind. Just wish I had that kind of money :). Lol, my lab has been on some death beds many times, and we pulled through for sure. Key question is, do you live in a super duper small town, mid sized cities, or a metro. If it's a metro, DM me and I will google, make the calls, and find a place for you. I'm a social worker, and pretty damn persuasive.