I found this for you at http://www.vanagon.com/problems/water-tank-key.html

OEM replacement water tank keys are available from:

Euro-American RV Products (AKA Delta Six Enterprises)
2506 Douglas Dam Road,
Sevierville,Tennessee 37876

+1 423.908.9384
+1 423.908.8132 fax

Key blanks
If you wish to make your own water-tank key there are blanks that will work.
According to Steve Sandlin of Steve's Lock Shoppe

"The key blank is an ILCO DM31. As a substitute, you can use the ILCO 1092 C
or Y12. This is a US manufatured equivalent of the DOM key originally used.
It is an exact replacement. The ILCO 1092C and Y12 both must be shortened to
work, but could be used in a pinch."

Thanks,
Chris Gronski
Toronto, Ontario,
'80 Westy "Pokey"
'87 Chevrolet Sprint 5-Door
'91 Pontiac Firefly Convertible

----- Original Message -----
From: "Graham Mingst" <GRAHAM.MINGST@CHASE.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, September 07, 2000 10:01 AM
Subject: lost key for water tank

> Hello List
>
> I cannot find my key for the water fill plug and I am going away tomorrow.
I
> know I can fill the tank from inside, but it would be more convenient to
do it
> from outside.  Without going to a locksmith can someone tell me if It is
> possible to force this little lock open?  I really don't care if it ever
locks
> again.  This is on an '85 Westy..
>
> Thanks
> Graham
>