I broke the delicate plastic lockring on my Runcam Arrow Micro so I designed one that was a bit more robust.
I used PETG filament so the lens could help cut the thread into the lockring as it went in.
You may have to print out several sizes to get it just right for your individual printer accuracy. I printed out 4 with a 1, 1.005, 1.01 and 1.015 X-Y scaling and one of them ended up working. I had the first layer at .3 and the remaining at .2 as PETG doesn't print well with any thinner layers with a .4 nozzle.