You might be interested in this one:
http://i34.photobucket.com/albums/d1...o/PHTO0019.jpg
and
http://i34.photobucket.com/albums/d1...o/PHTO0019.jpg
and
http://i34.photobucket.com/albums/d1...o/PHTO0019.jpg
This tank was installed in a very trick Myers Manxter, the owner had it made up custom by a major marine and race-car fuel cell manufacturer. The Manxter normally takes a standard VW fuel tank - so this should work in a Beetle and possibly another fiberglass buggy design. Capacity is ~13gl. Said the cost was $620 (as shown). That's dirt cheap if you look at what Fuel Safe will charge!
Jeff