4 spd Trans Seal??

[Alberta65]

Hey guys, Im trying to figure out a way of making a four speed trans seal, the thick gasket that goes in between the top of trans and bottom of trans tunnel. I know lmc sells them but I'm not paying to ship that to the great white north. Anyone have proper dimensions or material to use to make my own? Napa only sells thin cork and rubber gaskets but from what i can see this thing should be about 2 1/2" thick. PO has put in some house insulation so that sure as hell won't be going back in....

Thanks