I need some closed cell foam for wooden tree stand seats (Screaming Eagle), for squirrel repair.  Anyone got a source ?  Thanks in advance !

US Army sleeping mats.  They usually come in Olive drab.  If you can find them at a surplus store they are about $12-15 each though I have bought some for $7 that had a little damage.  Don't have a specific source for you though.

You might think about using a kayak seat. I use one of the Skwoosh seats in my kayak, with velcro strips on the bottom so I can pull it when necessary. I generally leave it installed, but if I lived among ravenous squirrels with no standards, I could take it inside with me.

  Skwoosh seats    

 CLC kayak seats and materials

Yes,the mini cell foam that kayak seats are made of is good stuff,usually in charcoal gray.You can also find it on the auction site in a variety of sizes and thicknesses.

There are some roll up exercise/sleeping mats that have some good foam.

Gardening knee pads at TSC or Wally World..
Sometimes on sale for $2.

I carry a closed cell foam Therm-a-Seat when I expect to spend time on my butt in snow or wet conditions.  They are easy to cut to size.

I've picked mine up on sale for just a few bucks each.  Full price is $8.99 at Mills Fleet Farm.

garden kneeling pads X 2

Good Suggestions.
I think the best thing is to just carry in one of those inflatable seat cushions.
Squirrels won't be able to eat it since you are not leaving it and it will be dry if it has been raining.
You can find them almost any where they sell hunting supplies. I think the name is actually "bun savers" and they self inflate when you open a valve.

Green kneeling matte x3. Home depot sells them for 4:00. Dark green.