I bought one from eBay. It would probably be cheaper and more time effective to get a second hand one by the time you’ve got the materials to make one and put it together.
I made one, found plans online, used leather panels salvaged from rear focus seats, to match the fronts I fitted to the 90.
Probably cost about a tenner in materials as I had mdf left over from something else, had to buy a piano hinge,a can of contact spray adhesive and 2 drain pipe sockets for cup holders.