Are you looking for just a tabletop extension that slides on to the end of your machine? Or are you asking about a table that you drop your machine into?
I had the tabletop kind for a while, till my shouders couldn't handle the height of a regular table anymore. I found a used Janome brand sewing table and love, love, love it. It wasn't cheap, but cheaper than a new one. It has the 36 " measure painted on, plus a little drawer and a shelf which are oh-so-handy.