In a message dated 98-05-04 01:55:14 EDT, glassewe@TELUSPLANET.NET writes:

<< Looking for a gas cap for a  '71 Van.  The original disappeared on
Halloween
 night last fall.  Tried  the auto recycles, parts stores and even a local
 antique car swap meet, with no luck to date.  The local VW dealer and
 Canadian Tire both tried to sell me a generic cap as listed in their parts
 books, but the were the wrong size.- to small in diameter - they would
 literally fit inside the filler pipe.  The pipe is 2 1/4" inside diameter.
  >>

you can buy them brand new from the vw parts suppliers here on the list.  or
RMMW or whatever..