Telescope Reviews: Mounting plate for SP/Carton rings

I've got a Carton 4 inch refractor mounted on an SP mount. Works pretty well. However, in order to do so, the Carton rings must be upside down. This allows attachment of rings to SP plate, but via only two screws (one per tube ring).

I need to find a plate that will attach to the two SP screws below, while providing holes for four screws for Carton rings (each ring is actually supposed to attach via two screws each = more solid). The two holes (per each tube ring) need to be 60mm apart on center. Also, no problem if the plate is extra long, resulting in rings further apart, since this would make the scope even more solidly mounted.

I've looked all over the place, Televue, AP, Losmandy, ScopeStuff, and others. I can't locate a mounting plate like this. I'd probably like to go with one of those plates that has umpteen holes in it to accept just about anything. Does anyone know of a good source for this (other than custom machining)? I could just keep scope set up as is, but I'd really like it a bit more steady.

Thanks,
Bruce