I know Vistaprint has/had a design platform that you can integrate into a larger website. I think it has a monthly fee. Hope that helps! Ken Clark Coach, consultant and therapist to entrepreneurs
Does your prototype require a flexible circuit, or is your prototype the printer itself? If the former, you can just design a circuit on your computer and then send that design to a service that will print it onto a flexible surface for you. Source: I designed and built an electronic prototyp...