Try here: http://brodak.com/wedge-fuel-tank-3-8-oz.html
The tank is mounted with the pickup tube (the one in the wedge) outboard so fuel will be forced to it. The other tubes extend to the other side of the tank...that is, the top one runs to the bottom, etc.
You fill into the top tube until fuel overflows from the bottom one.
Brodak bought the rights to Perfect tank some years ago.