Ages ago I had mimicked the "overhead scanner" with a mounted digital camera, but now I'd go with a mounted smartphone + light bars + bluetooth photo trigger. Scrolling through Bezos' was pretty depressing in terms of cost/quality and even a $150 device seemed like a repurposed webcam, with a sole non-free confirmed buyer saying it died after 3 months while freebies praise it lol. As long as you don't scan drawings/designs/comic books - just set lights evenly and that'd be enough, and even moreso if you OCR it and turn a scan into an e-book where visual fidelity stops to matter.

I don't know about buying, but the ones I have seen basically hold the book open at a 45 degreeish angle, to not damage the spine. Then you press the pages with a 45 degree set of glass plates. The actual "scan" is a camera of some kind that slodes back.and forth between the two halves on a mount.

same, probably when I'll have time in an other dimension I would love to make my own