Scopestuff do one.
SCT Female to T-thread Male Very Low Profile Adapter
This ring has female SCT Schmidt threads on one side and male
T-threads on the other side, with the lowest profile available.
Great for those applications where you need every bit of in-focus
possible. 1.485" diameter light-baffled interrior, 2.20" outside
diameter. Black anodized aluminum.
http://www.scopestuff.com/ss_talp.htm
Cheers
Dennis