Mike,
Plenty of them around but careful of the licensing procedure.
Those sampans are actually only used for Fish farms with a max capacity of 4 pax and HP of 15, but this is all a grey area under marine dept policy.
I can ask around for you but depends on what size engine you want and budget…u should check out Sai Kung waterfront and some of the fish farms, don’t expect them to be of high integrity and I would be cautious in going too far out or even around the headland – big seas and steep cliffs make for messy rescues. Another broker able to help you would be Terry Fung from Cyclone Runners – do a google check and give him a call.