My first reaction was:
. . . "There aren't any commercial single-lever portable paddles".
But there is the American Morse Equipment "Bushwhacker": http://www.americanmorse.com/bushwacker.htm
It's a true "single-lever paddle", with a well-defined center detent.
The builder's manual is online. AME uses plain bearings (dowels), not ball bearings. If their machining is good, that shouldn't be a problem. The advantage of that design: with support on both ends, those dowels aren't going to bend _ever_. The paddle looks rugged enough to survive the inside of a knapsack, and it's light.
I haven't seen one or used one, and I'd be interested in anyone's opinion who has.
I've been thinking about bases for portable single-lever paddles. I haven't seen anyone use a thin sheet of rigid plastic, long enough so that it's held steady by the weight of the hand and wrist, with the paddle bolted (or Velcro'ed) to one end. But that might work as well as a hunk of brass, and be a lot lighter to carry.
If you _really_ don't care about weight, the Bencher SP-1 single paddle is easy to disassemble. Open up the contact spacing, loosen the spring, and the paddles and contact arm assembly (the only delicate part) comes off. Put that in a small padded box. The rest of the paddle is pretty rugged. [I would never backpack something that heavy, but you might.]