Most or all of the immunization vaccines are free in united states with your insurance. You need to tell your doctor you require it for immigration purpose.
And  just take all the recent immunization paper with you to the USCIS approved doctor. But sometimes these USCIS doctors forcefully make you take vaccine from their clinic and charge you.
These are greedy doctors(mostly international). I tell you. the fee for a single is around $150 not $500. Contact and ask their charge first. They are real ass holes doctors waiting for prey like you.  and make you take shots which are all free from your insurance. First talk to your insurance about all the vaccine you need to take.

If such doctors miss something in the checklist, you can sue these irresponsible doctors who cares all about money only.
You do not have to take vaccine from USCIS approved doctors. They just have to approve the once you took from your doctor.