John.
There is a french seller on ebay, "sceno" somethingoranother, that often sells replacement shells for ideale saddles on the cheap. Not sure how easy/difficult this surgery would be to preform.
As for restoring them.
I've had a lot of success with brooks. The other day, at a local co-op, they had thrown away a b17 from the 70's that was almost flat. I asked for, and subsequently received the saddle.
Took it home, soaked it in water. Stuffed the inside with newspaper and cloths to for the base of the shape, then wrapped it with some paper tape and then duct tape over that for strength. Let it sit and dry for two days. When done the shape was back. Then I soaked in neatsfoot oil, several coats, adjusted the tension and lastly, after the neatsfoot was dry, did a layer of saddle soap.
This was my second time doing this and it came out great.
Sean Flores
San Francisco, CA