I gotta run, so this will be short.
Consider a folding hand truck. I have one from when I played with ocean going boats. Check west marine web page. Not cheap, but folds into a small package (about 26"x 15" x2" if my estimate is correct) and holds in excess of 200 lbs. I once pulled the engine from my boat and hauled it about half a mile over gravel to my truck. No problem (huff puff), Large wheels, very strong.

Still have it tucked in the camper and we use it a lot.

I will try to track down a url, but it might be a few days.