Does anyone know where I can source cardboard oven proof and microwave safe pie dishes and if these are even possible?
I'm not sure whether they are sold for consumer use, but I can say that Amy's brand pot pies come in a cardboard pie pan with instructions for microwaving or baking in a conventional oven. So they do exist.
Whether such pie pans are suitable for start-to-finish creation of a pie is another question, I'm fairly sure the Amy's pies are partially prepared and then transferred to cardboard pie pans (possibly after they're frozen).
For home cooking, a glass pie pan would be an option if you need to bake a pie in the oven and then heat it later in a microwave. Depending on your oven, you may need to be careful to place the pie pan on a metal tray, or put a metal tray on the lower rack below the pie pan to prevent radiant heat from over-cooking the lower crust of the pie. (Edit: On second thought, a baking stone would probably provide a better radiant heat barrier.)
I am looking for them as well for a restaurant venture. What I have found are some disposable pannetone molds in various sizes. I think I'm going to try them to see if they hold up. They seem to average at about $0.50 per dish. Good Luck to you!
You can look under the packaging of products in frozen food aisle at the supermarket. They all have the name of the company who produced them. You can try contacting them.