I got mine from Sew Steady. I think they made it just for my machine, as it fits perfectly. It took about 2 weeks to get here, but I believe it said to allow three weeks. When I ordered it, I simply had to tell them what machine I have and what size I wanted. Folks on this board advised me to buy the biggest one I had room for. That was good advice.
I am quite happy with it. I had to get used to moving it when I changed the bobbin, but that may be peculiar to my machine (Pfatt Expression 2.0). I think my extension table is 24 inches by 18 inches...too lazy to actually measure it.
It was either $65. or $85., can't remember which. I bought it in October, and there were smaller sizes that cost less.
Hope this info is helpful.
Dina