HVAC Foam Seals

[Flyman 27]

I am trying to find a source for the soft, open cell, sticky back foam used around the plenums & outlets to stop air leaks.
I have tried standard foam insulation, but it isn't soft enough and the sticky back doesn't stick to plastic very long (like a couple days).
I have looked for kits with the cut shapes, but none are available as far as I can find.
My second choice would be to find this exact soft foam that is used in cars. It can be in strips, sheets, etc. I don't care, I just need to seal things up, I have a lot of leaks all over the place.

Anyone know of a product & source?

Dan