Used at e-bay. I've seen Brooks and the old Schwinn types. Niether are cheap.
I remember you or someone posting about repairing "mattress' saddles. Since then I've read that better models came with Brooks anyway. New sprung Brooks saddles cost 110 to $140. Low cost saddles can be 5 to $50, used or new. Brooks had a brown & white one for Raleighs etc. One's in e-bay now; who knows what it will end-up at. Under vintage parts and accessories.