NAPA carries the Dynomat, it comes in a package of 5 , 12 inch by 12 inch for $21.99 part number BK 825-6300....
or there is a product available from Lowes or Home depot that is designed for roofing repairs, I understand it is very similar, not sure what its called but have heard of guys using it for this purpose...
I'll see if I can round up some info and post it for ya.....