If your part of a pinball community where you're at in TX I'm sure someone has a burner and would happily loan it to you. Hell, if you want I'll send you my burner if you kick me a few bucks for shipping.
As for that French site that has the roms it is definitely legit. https://www.flipprojets.fr/Freeplay_EN.php
There is a guy on pinside that has most all gottlieb rom sets. Not sure he would appreciate getting called out publicly. I'll DM you his info. If it were me I wouldn't pay for preburnt roms. Owning a rom burner has come in pretty handy. Everything I learned about rom burning came from this video

I'm sure someone will correct me if I'm wrong but I think the rom files on virtual pinball sites are usable also and can be burnt to roms.