I had never heard of the darn things until they showed up in a conversation a month ago.
I bought one locally last month. It is the M116A1, I'll post a photo later. The guy that I bought mine from also has the older, smaller, one for sale for $300. If anyone is interested I'll see if it is still available and take some photos. It was raining the last time I was there and I was busy getting mine out of the muddy field (playing with the CUCV 4x4).
GL had several of both styles for sale in the past month.
Speaking of which - I didn't realize that the M1009 has the smaller electrical connection (for the 1/4 ton trailer) I couldn't get the M116 connection to fit so managed to drag it home without lights. If anyone has a manual it would be interesting to see. I do have TM 9-2330-202-14&P in pdf, but it is for the M116A2 and later. Different support leg, hitch, etc. Would be interesting to see the manual which has the tool trailer info.
I was thinking of a combination camping / service trailer. Generator, air comprerssor, plus bulky camping gear, automotive tools, etc. This spring I'll start with new hinges, sand blasting and paint, then go from there.