I found out how difficult it is to empty a SOF of water even with very large float bags. So I need to make a sea sock.

Since it is going inside of a F1 which has a combing with a small lip, I thought I would make the soak out of the thinnest material possible at least over the top of the combing and reinforce it around the wear areas.
So here is the real question, can anyone point me towards a mail order/inter net source for cloth that might do the job?

Thanks!