[Roadsters] gas cap

[twokeelya at gmail.com]

Last night my locking gas cap was removed from my roadster and all the gas
siphoned out. Finding the correct cap (one that goes on) has been a real
adventure at all five auto parts stores in town that hasn't been solved. Is
there an equivalent over the counter cap that fits out cars? I'd buy one
from Datsun parts but I need it NOW. tried at least 20 different caps and
not one will turn.
Thanks
Richard