I have one that is threaded if that is what you have. I have seen numerous styles of after market caps on these cars. Just have to take a look at the parts places.
Parts place does not have one, can you tell the parts store were you got your at, my is a quarter turn also. I seen one on ebay from a place in Southampton Pa. Want to call but I cant find the phone number. I will keep looking. thank
Advance auto has locking caps that fit the Rabbit.
they don't look stock but they work.
'91 Golf gasser converted to a 12mm pump, M-TDI.
'84 1.6TD Rabbit with a VNT-15 turbo, still setup to run on vegetable oil.
'84 GTI with 1.7TD pistons and intercooled.
2003 TDI wagon
2000 TDI Jetta.