Please help
 

I have a '92 cadillac deville, V8 PFI, and I lost the oil filler cap. When I go to the internet, or the parts store, all I can find is a 1 1/4" filler cap. That is not it, mine has a 1 1/2 " hole, and was a screw in. Seemed to be OEM, with a silver scalloped top. Does anyone have a hint of what part this is ?
I tried the V8 engine subforum, it was a ghost town.

Best Regards,

Jack