You could try Chicago latex. They ship neoprene. I've used it, and it works out well, but with a 2 part "closed" mold (I did a set of large man sized hands in a two part mold and let it cure for 48 hours with air and moderate heat) it was a disaster. The hands were patchy -- thin in spots and thick in others, and it was very difficult to de-mold. I had to scrap them and pour new ones in latex -- which worked out fine. It may have been my mold -- residual mold releases inhibiting the absorption, but I have found that even in molds that had virtually no mold releases in them, I got some patchy spots -- including open faced molds.
I'll follow this up with Chicago latex's contact info.