I thought i could find this picture i saw for you but i couldn't....but it is pretty simple. At Lowes/Home Depot they have these insulate sheets that are 4x8, some have reflecix and others don't. IIRC one sheet is only like 6 or 7 dollars (the reflectix ones like 12 dollars )and it would only take 2 sheets. Cut out 4 sides big enough to fit around the smoker to have some dead air space...maybe 30" x 36" or appx. fit them together in a box shape and tape vertically along the edges to hold them together with good foil tape or duct tape. Notch out some air inlets on the bottom of each side so air can draft in.
You don't have to worry about the insulation melting because it wouldn't be touching the smoker, lay something heavier over the top (offset it so exhaust can escape) to hold it down in place...i suggest cutting a piece of durarock.
You could make something similar out of wood...the most important thing is to have dead air space and go all the way around the smoker and have a top to let exhaust out.
Keeping wind off the smoker is the most important thing but if you can get a box around it that would be even better.