TD Directory or the folks from Playthings can help. But frankly, we think you're facing an uphill battle -- not just finding the manufacturers -- but getting permission as well.
You've got two choices: You can proceed without permission or you can use toys that you can verify are no longer made or promoted. Proceeding without permission may be fine, particularly if the manufacturer is gone. The good news is that you probably won't have to be concerned about trademark infringement because you don't know the toy's name. We also think you have a good chance of avoiding copyright infringement assuming your use is transformative. And that perhaps you may even be able to argue that the toys lack sufficient creativity to be protectible under copyright law at all. PS. If you're looking for old toys that may safe to use, check out sites like this.