Out of curiosity, are you discussing the type of 'single' wooden sleeve which can house either a Stereo 70 or a Stereofetic, or is it a 'double' type to house both units, similar to those used to house the Quad 33/FM3?
When I was searching for a sleeve to house my refurbished Stereofetic, I had to make a return road trip from Torquay to Truro, to collect a really dirty and 'unloved' Stereofetic, which I had purchased via 'e-pay', however, it was complete with a sleeve and the 'fixing' wingnut.
Much later, I noticed that on the 'Layers of Beauty' website, there was and still is, an image showing a 'replacement' sleeve for a Troughline, which I assume is of similar dimensions, and can presumably be made to order in a veneer of your choice.
If I'd have known that at the time, it would have been less stressful and more cost effective to order one, given that the sleeve that I collected certainly wasn't in pristine condition. Plus, I now have yet another piece of 'junk' (according to S.W.M.B.O.) which I can't quite bring myself to scrap.
Merry Christmas
Mike Kelshaw