I've been using the
EZ Rest which is a mahl stick sort of thing that clamps onto your easel and pivots around to wherever you want it.... Since it's attached you don't need to hold it with your free hand. It's maybe a little further out from the canvas than I'd have prefered at first, but I've gotten used to it and feel lost without it now.
I also use a cane when I'm painting on my travel easel, but am much less comfortable with it.