I have a Beldray one, but I bought it in the late 70's and so I doubt it's still in production! It's simply a metal board with a u-shaped foot that swings backwards and into two metal clips. It's padded and covered, of course, and I've redone the padding and covering when need has arisen.
Just checked and Brabantia do one that is virtually identical to mine. Definitely worth having for shirt-making. Not so good for setting in jacket and coat sleeves - for that you're better off with a ham or one of those pressing mitt things.
Argos do a Leiftheit sleeve board but claim it weighs 80kg, so maybe not such a good idea