i went and got got the plexiglass from home depot..made a paper template on the machine,where the insert goes, and DH cut the piece out. total cost? under $20.00 bucks. 250 gauge(1/2 inch thick) 18 x 24. i got the legs from home depot also..they screwed in, and are adjustable..i can take a picture if you would like. I have it for my janome jem..my other janome is in the sewing table.
You can do the same thing with wood..you would need to sand and clear coat it to make it smooth, so the fabric won't snag.
It is a big improvement when sewing, and especially when quilting..