I would recommend to purchase a 6 X 12 Horseman or Chinese 120 Roll Film Back for the Cambo Wide 650.
The Schneider 65mm will give you the equivalent to a 21mm Lens for 35mm Film.
You wouldn't be able to use the 65mm on a 6 X 17 Camera.
Maybe it's not 6 X 17, but at least you can use what you already have, a Chinese 120 Roll Film Back runs at about
$200. on Ebay.
Just a thought for in the meantime you find what you are looking for, All the best!