For Christmas I gave myself an inexpensive thermal imaging camera. So I got it 10% cheaper. I am very satisfied and it is more than sufficient for my needs. Except for the precise diagnosis of pcb electronics.
I found a suitable solution for this: a ZnSe lens with a diameter of 20mm and a focal length of 50.8mm.
Find the ZnSE lens on Aliexpress (Affiliate Links):
I recommend the first one. In my case it holds up well enough. When you push in the adapter plate you can also hear a small clicking noise. When I shake or tap it it doesn't fall out.
If this is not the case for you or you just want to secure it better, you can use one of the variants with the clips.
The lens must be pressed into the adapter plate. If the lens doesn't fit in, just file it up a bit. Normally the lens holds so tightly in the adapter. The ring can still be attached. Possibly with just a little bit of glue. But normally the ring clicks into place cleanly. This also protects the lens somewhat.
Print instructions:
Supports: Only for Version 2 & 3.
Brim: Optional, only if you have adhesion problems.
Find this Project on Instuctables: https://www.instructables.com/HIKMICRO-E01-Eco-Eco-V-Macro-Lens-Adapter/
Informative video for better understanding and dealing with thermal imaging cameras: