Do you paint directly on T-shirts or do you just paint on the screen? I have not seen such streams yet.

Sorry, I can't donate, but I can give you an idea how to create it easily. I know Printful, where I once made custom stickers. Click https://www.printful.com, you can create T-shirts, hoodies and other things in their design maker. By the way, you will not need a warehouse for the merch, because the employees will immediately send it all over the world