Ok, one doctor's visit and four phone calls later... it looks like it'll be covered!
Details, in case they help:
My doctor said he does not carry the vaccine but I should contact a travel clinic. I found a travel/urgent care clinic that does pre-exposure rabies and takes my insurance (Blue Cross Blue Shield PPO). I called my insurance company to ask if it would be covered, and they said that immunizations are generally covered 100% and I wouldn't need to provide any paperwork, but I should get the exact billing code and call back to be sure. I called the urgent care clinic and they gave me the billing code. I called my insurance company again and gave them the code, and here's where it got a little tricky. The customer service rep put in the code and said it came up as a rabies "injectable oral medication." Since that didn't make sense, she then tried a whole bunch of combinations. Even with a specific billing code, how much I'm charged can depend on if the visit is coded as out-patient or in-office and if it's coded as an immunization (covered 100%) or an injection or injectable oral medication (I pay $500 and then the rest is covered at 80%). Eventually she figured that in this particular case, it shouldn't matter whether it's in-office or out-patient and that since it is an immunization, I should ask the doctor to code it as one and not an injection (and she said the doctor will as long as they think that's appropriate). I called the clinic back and was able to confirm that it will be coded as an immunization, so it should be covered 100%. Huzzah!
I hope this helps! For anyone else trying this, I would recommend finding a travel clinic that does rabies vaccines and making sure they take your insurance and are considered in-network (may be difficult if you have an HMO, but the clinic I'm going to is in-network for some HMOs so it's worth a try). Ask them for the billing code, then call your insurance company to ask if it's covered. You may have to go through something similar with immunizations vs. injections and in-office vs. out-patient. Feel free to PM (or ask here) if you have any questions.
EDIT: I'm annoyed with myself for not even trying this earlier. I used to volunteer at a wildlife clinic that would only let vaccinated people work with raccoons. I missed out on some baby raccoon snuggles!