Years ago I ended up buying some inexpensive, simple, yet fairly heavy duty monitor arms and stands. They're robust enough to let me attach more than just the monitor arms to, I started playing around in Fusion360 and came up with some handy clamps for them that let me attach a variety of things to the monitor stands.

This one is a mount for an Ikea Tertial lamp. It's not fancy, but it works very well.

The camp needs 2 m3x18mm bolts to tighten it against the monitor stand. There are integral threads in the .stl file, so you don't need to do anything other than put the bolts in and tighten them. You don't need to go overboard when you tighten the bolts - once you've tightened the bolts enough so the clamp doesn't want to rotate, that is all you need.

I used 18mm low cap head bolts in the pictures

The monitor arms are 1 3/8" / 35.25mm in diameter. They are sold under a number of brand names, but I got mine from Allcam off of ebay and Amazon here in the UK

I've made several different types of holders that use the same basic clamping system. I'll upload them over time, just in case anyone else out there might find them useful.