I'd guess that there would be a good market for that item at the $320.00 price. The extra $200.00 shipping would kill it, though. I imagine that there are import duties, too.
Still, when I had my yaks, that would have been a great addition. I put a trolling motor on a couple of them, but, when you add in the weight of the battery, this device has to be a lot lighter. Not THAT much more expensive, either, without the duties and shipping.
Now, if you could just buy the pump, then any gas edger motor would probably work out fine.