Hi Poita,
I have just purchased a PST and wanted to check for binoviewer compatibility and found these positive web pages.
Siebert manufacture them
www.siebertoptics.com/SiebertOptics-H%20alpha.html
There is a dedicated Denkmeier OCA and a 'Universal' binoviewer OCA. I have Williams Optics binos. Review home.primus.ca/~gmuller/binopst.html