spring insulators,pads isolators?

Anyone know where to get the pads that go under the springs front and rear for a 61 special that doesn't cost a arm and leg?.  Has anyone made their own with 1/4 polyurethane mat and how did that work out?

Eaton Detroit spring sells the rears for the Buick for $9.95 each. When I got front and back coils for my 62 Cutlass convertible they only came with the rear coils. I don't think the front coils have isolators, but I may be wrong or it may be a Buick only thing.