I know there is GI style soft canteen out there. It was billed to be less bulky, lighter, and not bruise paratroopers who landed on it. A guy I know had one - the issue was that it leaked after repeated hard use. The seam parted and it became useless.

Personally, I ditched the canteens in favor of a camelback. It holds just as much if not more, is easier to carry, fits my water filter, and it handier to drink from.