I have been looking for a while for a 2” erecting prism that does not break the bank for occasional terrestrial use of my 4” refractor. Mostly what I found was in the $300 ballpark, and that was more than I was willing to spend for this application. Recently I came across a promising-looking unit on Ebay for $63 including shipping from China. Search for “2 Inch Erecting Image Prism 45 Degree Metal Diagonal Corner Zenith Mirror A Z4T3” from edieret-us”.
It took about 2 weeks to get here and I have to say it fits my needs very well. Pretty solid, with compression rings, not too bulky (as 2” diagonals go), and it even comes with a little pouch. The only thing I did is exchange the set screw for a shorter version. The original one was long enough to fit through the 1.25” adapter, so in 2” mode it was sticking out.
I tried the diagonal briefly in the daytime and the view was nice and clear. I did not notice any vignetting with my 40mm Paragon. The aperture near the prism is only about 1.25”, but I think the light cone is narrow enough there to not cause issues?
Overall a nice piece at a good price, so I wanted to share.