i saw this posted on the bge forum the other day and i just ordered a 0.125" thick 1" x 50' roll. looks to be the exact material sold by bge, but a whole lot cheaper. scroll down to the aramid fabric strips, aka nomex:
here's the thread where i installed a bge nomex gasket on a large egg awhile ago:
i'll post an aramid fabric gasket install after i receive it. gaskets are considered a maintenance item so replacement is inevitable.