I found that listed in the plans; Once as P/N F-1094C and once as P/N F-1094C-L. I couldn't find it on Vans web site or ACS. Guess I'll have to call tomorrow.
Go to Van's web store and search for "Rubber". It comes up with options for 10", 12" and 4'. This is what you need. The "-L" is the part you create for the left side once you cut it to length.