I once again turned to my friends at http://www.jamestowndistributors.com for all my fiberglassing needs. I ordered a gallong of West Systems 105 epoxy, and a quart of the 205 fast hardener.
This is the same stuff I used when I was making the mother mold for my cape about a year ago. The stuff is very easy to work with, doesn't smell awful like common off the shelf fiber glass products do, and is reslient as all getup.
It is a tad on the expensive side, but when you buy at Jamestown it's about half the cost that I have seen it go for in stores.
I will use this to make the negative mold of the cape material. The output from that mold will be used on the boots.