Denny,
I bought all of my spring parts at a major spring shop nearby. The tech working on my springs said his shop can't order the seals. He gave me a long neoprene seal and told me to put a drop of oil on the knife and cut them to fit myself.
I think I have seen the cork ones around though...
By the way, my springs were about $455 to re-work with the shop bending new mains for the front and new bushings on all the ends. The truck sits nice with no sagging on any of the corners.
I am hoping that by spring, I can have her back on the road for a test..