Bomar has the gasket material. You can order from their website, but its a ridiculous price per foot.
I took my forward hatch off this fall and brought it home.
There is a rubber place in Cleveland that hopefully has something that will suffice. Will take the hatch to them and see what they say.
Currently I have no gasket on the hatch as I ripped it all off last year and tried to use some crap from the auto store. Big mistake!
Here is the site w/ the spare parts.
Bomar-Karl
1986, 32' Sedan, twin 360ci, 275hp Chrysler's w/ K&N flame arrestors