http://wiki.arcadeotaku.com/w/Namco_System_246/256#Optical_Drivecan suggest any model that can use on system 256 ?
This kind of practice seems a little dishonest to me, unless they're specifically selling it as a System 246/256 drive.Ebay is really your best bet. Don't buy something expensive. Just buy something used and if it doesn't work, tell the seller it doesn't work correctly (i.e. read discs, tray doesn't come out). Most of the time, they'll just refund the money without having to get you to return it.