I think I used the search terms: "Spare Tire" "Gas Can" (and "Gas
Tank") on eBay to find mine. There is an old VW one on sale right now
(at what I think is a ridiculously high price):

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4555241048&category=42606&sspagename=WDVW

Photos at 

http://albums.photo.epson.com/j/AlbumIndex?u=3009767&a=31756786&f=

There is also a Mercedes 190 can:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4555396082&category=42606

Be sure to check what diameter wheels they are intended for. I bought
a tank intended for a BMW with 15" wheels and it fit perfectly. I have
no idea if the tanks I mentioned on eBay will fit, nor do I have any
assocation with them. If you are interested in the items contatc the
seller not me.

Chris

On 6/9/05, Michael Elliott <j.michael.elliott@gmail.com> wrote:
> A couple days ago, Christopher Gronski wrote, "I have a round 9L gas
> emergency gas can that fits inside my spare tire under the van (15" SA
> Rhein Wheels)."
> 
> Sounds handy. We want one.
> 
> Where does one find round gas cans in the U.S.?
> 
> --
> 
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 83.5 Westfalia: Mellow Yellow ("The Electrical Banana")
> KG6RCR
>