Panasonic?
I have been using a Panasonic 2AA travel unit for the last five years when I travel. I also have their standalone rechargeable unit which share the same tip system. This unit adds pulse flooring as well as Mix air into the water flow to maximize the cleaning capacity of one refill of water to the tank. It is half the size and weight of the Waterpik.
It was about 500HKD at a Panasonic authorized seller.