Well I was looking for a cheap version of such a thing only to find out that these things are expensive even on ali.
I had a round piece of glass salvaged from a broken torch what was the perfect size as a semi reflector: I decided to give it a go myself.
I took a picture just to see if I had tone the measuring more or less right and the camera would focus on the reticle. No camera holder for the moment so the picture is not centered correctly but the reticle shows up half decent.
The adapter has a dovetail so the camera mount can be custom made for whatever you need.
Once I have everything working right I will make the housing for the glass suitable for a rectangular piece to be salvaged and cut from one of those cheap picture frames. Actually the thinner you can get the better so the second reflection will be indistinguishable from the first one. Best solution would be to find an oversize microscope slide cover because the standard 18x18mm are too small for this job.

Should you want to actually use this as of now you will need a small glass disc 37.5mm diameter and 1.5mm thick. Alternatively a brand new clear lid from a cd case might do the job well enough.
Currently the adapter is designed to fit a 43mm eye piece on the scope, if your's is smaller you will need to make circular shims. If your scope is bigger write me a PM and I might make another STL that fits your scope.
The internal passages need to be black preferably mat.
I took another picture this morning with the adapter properly fixed to the scope, the building in front of me is some 35m away and it is still dawn so the light is not good and the scope is a cheap Chinese Nakida 3-9x56 ... considering the the cost to 3d print this adapter compared to one off the shelf and the low end scope I'm satisfied. I consider the main body definitive aside from some minor changes to the camera fixture.