The 2065 bulb is indeed a #57 bulb available from any auto parts store (see below). They are nominally 12V, but are actually rated for 14V. They can be run at higher voltages that our trains use at a cost of a somewhat shorter life (stock life is about 500 hours rated). You will be just fine replacing with another #57.
As for what you are calling the class light, Lionel refers to it as the running light and is part number 2065-16 which @S AND W lists:
If you are looking to one stop shop, @S AND W also has the #57 lamp you need:
Automotive listings for the #57:
https://shop.advanceautoparts....2-57llbp2/10030922-P
https://www.autozone.com/elect...bulb-57ll/964974_0_0
https://www.napaonline.com/en/p/LMA57
