Is this what you are after?
http://www.scopestuff.com/ss_taep.htm
2" Eyepiece Barrel to Schmidt Thread Adapter
Fits in place of a 2" eyepiece, but has male Schmidt threads like a SCT visual back. Adapts SCT visual back devices to 2" backs, focusers, refractors, etc. Male Schmidt threads fit SCT focal reducers, diagonals, turrets, etc. Threaded for 2" filters. No "safety recess" to interfere with compression rings. Black anodized aluminum.
Cheers
Dennis