The NATO cable with two adapters is the most versatile setup. It will let you slave from any configuration to any configuration. The old 2 pin cable cannot jump to a NATO connector. Due to the configuration of the ends, no adapter is made.
My deuces have both NATO and the old 2 pin plugs just to make life easier. The vast majority of M35s have the older 2 pin setup (if any)
The going price for your first one is "whatever it takes". $95 is not outrageous for your first cable. Now that you've got one you can be more patient with subsequent ones.
Since I don't think you can have too many, we've got 2 ea 50' NATO, a 20' NATO and 2 or 3 ea. 20' two pin cables. We've got a few on loan to new MVers, too. I like to have one on every vehicle with a 50 footer for the shop. I also keep an extra adapter in every truck with a 2 pin connector.
I typically snag the 20' two pin ones for about $30 and the NATO ones for around $50 at shows. My last 50 footer was bought at Aberdeen this year for $90.
You made a good catch. I like your copilot.
Lance