I hear you about the low back......tables good to eat at are not good to work at.
I found a set of folding, adjustable length, metal saw horses at Lowes some time back. I grabbed a used hollow core door and screwed the horses to it and glued some cheap flooring to the top side. When it is folded up and laying in the bed of the truck, it is only about 4 or 5 inches tall. When I open it up to use, the legs will stand up well past 40". This will not give you any storage space but it is very easy to move and store.