I have bought it in a roll. Most decent HOT ROD shop should have it. I did my 40 Ford with it and it has about 35 thousand miles on it since it was done. Still riding nice ... according to the new owner.
I got mine from Speedway Motors in Lincoln NEB.
This is from their ad
Equal partners in a smooth-riding leaf spring suspension are quality shocks and friction-free movement of the spring leafs.
This special compound of poly-vinyl plastic has a very "slippery" surface. This works as a permanent dry lubricant that eliminates interleaf friction and squeaking. It also features a small lip to keep it in place.
One roll does one cross spring. 20 ft. roll.
Go here ... less than 20 dollars