Suppose Alice has a verifiable (message, signature) pair from Cedric, who would not cooperate and routinely uses an algo (ecdsa, eddsa, rsa, or insert yours here) to sign messages.
Alice wants to interactively prove to Bob she has that (message, signature) pair with the valid signature, obviously. It doesn't have to be "zero-knowledge" - she might divulge bits and pieces, but it shouldn't be less hard for Bob to recover complete (message, signature) pair than for Alice to forge the signature altogether.
Obviously, Alice and Bob both have Cedric's public key. I look for an interactive procedure and stochastic proof. Preferably with existing implementations.