According to my handy dandy Brecoflex binder, Linatex, Super grip, Correx gum, PVC Blue, Polyurethane, and a few others have the highest CoF's.
I could go through the whole catalog and tell you what your options are, but that'd take way too much time
Go to
www.brecoflex.com and order one of their free product catalogs. They'll send you a binder with whatever inserts you choose. They sent me mine in two days, if I remember correctly, and they come with a wealth of information.