I got a Arrow Bertha this year for Xmas. It has the back extension, and the sides fold down so it becomes a small cabinet when not in use. it was 799.00 but it was the only one my 820 would fit on -You can get customer inserts that are custom made for your machine. I am very happy with it but it did take DH a while to put it together.
You can find them on the net even Walmart's web page but the Arrow website sometimes have sales where you can get the insert for free.