When I looked, most parts-house available sensors are small and even a 1" format sensors are pretty dear. MFT, APS-C, etc. were a multiple of a complete entry level interchangeable lens camera. For a pinhole camera with a small sensor, it's going to be hard to frame a specific subject because the sensor's field of view is tiny. Even a wire viewfinder will probably struggle with framing due to parallax. Basically the low cost sensor for pinhole photography is photo-chemical film.

A hacky alternative for a might be modifying a flatbed scanner. Just step the photo array slowly enough that there's reasonable exposure at each point. The good part is that a flatbed scanner is a stupid big sensor and there is some literature for hacking them. But for a pinhole, I'd expect the exposures to be rather long even for pinhole photography.