Hey, ive also been looking for some black foam with no success, ive rung all the above, checked every big DIY center in the land to no avail. Unfortunately i cant just paint it because im doing something different, im creating a background for my frog tank by using black foam and laying a mixture of pete/coco fiber and moss on the top before it cures to give this effect:

(see fancy background 3/4 down the page)
http://www.brianstropicals.com/building.html

Ive tried it with white foam and it just doesnt work half as well, ive found lots in the US but you cant get it shipped over on airplane so no providers sell it internationally.

Please help,

Chett