I'm not aware of any simple, inexpensive way to do this but it can be done. I have no experience with the A-P focusers and don't use binoviewers but I do use both Baader ClickLocks and QuickChangers.
I'm not aware of a captive ClickLock. It takes two hands to rotate the diagonal but it is much better than fiddling with 3 thumbscrews. I use a ClickLock on my VMC200L just for that purpose. But I repeat - it is not captive.
For adding captive rotation I use both the standard and the HD versions of the T2 QuickChangers between the focuser and diagonal to provide a rotating feature. They are captive - although if you loosen them too much they will separate. I use them with the Baader T2 prism and T2 BBHS diagonals. Loosen slightly, rotate, snug back up. Works great. If you don't mind a 35mm aperture restriction the simplest way is to convert to a T2 diagonal + Quickchanger + 2" nosepiece. I understand some binoviewer users then attach the (Baader?) binoviewer to the T2 diagonal with another quickchanger. I use a 1.25" eyepiece clamp. You can also use a 2" eyepiece clamp on a T2 diagonal (Clicklock)
Another way is to assemble a rotating section from a quickchanger: https://www.baader-p...6a-and-07).html plus a 2" nosepiece: https://www.baader-p...2-part-16).html plus a 2" clamp to hold the diagonal: https://www.baader-p...ece-clamps.html. This will require about 2" of in-focus due to the length of everything. On the order of $300 for the pieces This has a clear aperture of about 37mm.
If you want a larger clear aperture Baader does make a 68mm version of their QuickChanger (68mm Zeiss thread) but very expensive. The US dealers don't seem to stock it either. This would work with 2" diagonals. Clear aperture will be limited by your diagonal.
The two pieces are: https://www.baader-p...lamp-only).html and https://www.baader-p...).html?___SID=U.
To these two pieces you would also need an adapter to the A-P focuser. maybe one of these (I don't know): https://www.baader-p...).html?___SID=U or https://www.baader-p...).html?___SID=U and also a 2" eyepiece clamp to grip the diagonal.
If you are willing to change diagonals, and need 2" then Baader offers a version of their clicklock diagonal for use with the 68mm thread quickchanger: https://www.baader-p...ad-(zeiss).html so you could skip the 2 inch eyepiece clamp.
You can also convert the 2" Zeiss prism and BBHS diagonals using yet another adapter.
All these pieces using the 68mm Quickchanger are very expensive.
Sorry for the long answer - I wish I knew of a simpler solution. Hopefully someone else will know of a better solution.
Edited by Don Taylor, 14 October 2019 - 10:39 PM.