Flexible closed-cell foam - pourable

I found a local source of closed cell foam, in rolled sheet of 60" wide and 3/4" thick, I forget how long, but the log is 36" in diameter. It's about $500 a roll with shipping, that seems expensive to me. If you want a 4' x 8' sheet it's over $100 closer to $200, and there are more than five sheets in a continuous roll.

I've read about two-part liquid, expanding "rigid" urethane foam which is closed cell, pourable foam, and will resist the absorption of water.

QUESTION
Is there such a thing as two-part liquid, expanding flexible urethane foam which is a closed cell, pourable foam, and will resist the absorption of water?

The lighter and lower the density the better for my application.

This is a home brew design/experiment, so funding is very limited.

NOTE: I've been looking into this topic for a while now and getting nowhere. And what do you know, just found this:

http://www.rubbermoldcompounds.com/special-effects-supplies.htm
FlexFoam-iT!

..............now I just have to poke around and see if it's open or closed cell.

I could use any information or suggestions on where else to look.

 

I called up US Composites, best time to call in early in the morning. The guy on the phone was honest and said he was not the best person there to talk to (I called late in the day). He had me going - said they have "flexible foam", but closer review of their site shows only pourable "rigid" foram. Guess it's flexible until it cures, don't know what he was thinking.

Anyway 2lb foam is the lightest and cheapest.

http://www.uscomposites.com/faq_foam.html