I built a roof over most of my ladder stands with metal conduit and radiator hose clamps. I just bend it into a big U and clamp it to the sides of the "cage" around the seat. I put a piece of tin (3' x 3') on top and attach it with bolts (actually i put tin there and make marks where the bolts need to be with a sharpie, then drill and put a bolt and nut on the tin then put bolt through conduit and another nut). I can also add some burlap or screen to hang down to hide me somewhat.

I like them more than umbrellas because it is always there and the deer get used to it...