Mr Acorn made me one from a spare piece of kitchen worktop.
It has sections of wooden curtain pole for legs, and is extremely heavy - which is good when it's in place, less so when it needs moving! The front edge - which you can't see in the pictures - is curved, which lets the fabric move fairly easily, and there is a very slight slope from back to front, so that it lines up with my machine (other machines may not need this).
I lined the inset bit, where the bed of the machine sits, with felt, to protect it.
The original thread is
here.