Welcome Michael.
I do not know of any marketplace. There are a couple of Facebook groups on the film scanning subject (Budget Film Scanner and DIY Cine Film Scanner Makers). Tscann 8 is quite popular as a DIY project, and a branch in github mentions a Discord group.
Two broad groups in DIY:
- Using an existing projector and setup a camera trigger to capture frame by frame. Usually via a reed switch, and slowing down the projector motor. A variation is to replace the motor with a stepper.
- DIY projects that do not use projector parts. For example, Tscann-8 which has been done by a few builders.
On the second group, if you have access to a 3D printing shop and drilling (or laser cutting), you would not be starting from scratch.
The scanner that I built -in my opinion- is a bit simpler transport than Tscann-8, better results, and longer scanning time. One of my goals is to provide documentation as open-source for others to build it (similar to what Tscann has done). But until now have been using most -of the limited time I have- improving on it, mostly to get the scanning done at the quality that I was targeting (not the scanning speed). Mine is in the low-cost group, probably under $800 (with ebay lens).
There are some higher-speed higher-quality higher-cost (mostly the camera) projects here, such as Roland’s All format scanner.
In summary, the short answer is no marketplace, but the long answer is maybe some alternatives to look into.