Where to Get Type D Gasket?

[sandgrubber]

I have a 1971 Caravel. The window (and door) gaskets are shot. The existing window gaskets are between 3/8" or 7/16" depending on whether you go high or low. Vintage trailer supply sells what they call Narrow D Seal at 3/8 width, which seems ideal, but it only in 10 foot lengths, and I'd rather avoid splices and wastage. Where can I get the same stuff in longer lengths?

[cameront120]

Inland RV in California. They carry it in different sizes for both windows and doors:
Inland RV Center Inc.