After watching that 11-minute youtube with the sail rigged ocean kayaks somewhere off Tasmania, did you know the
www.topkayaker.com located in Ossipee NH seems like the place to get a mast and sail for your $144 Walmart kayak.
By the way, if the kayak is 12' long and has a sail, then it probably needs to be registered in NH which costs about $45/year. Oh well ....... if you can afford a kayak with a sail, then the $45 is probably no big hurdle. Displaying the registration stickers without displaying the 3" high hull numbers on both sides of the bow is ok for sailboats from 12-16', so that is basically a $45 annual fee stamp.
Am not too sure about kayak sailors longer than 12' needing to be registered ....... could be one of those rules that almost never gets enforced ....... and can probably go 12' kayak sailing like this without the sticker ...... saving $45 ..... ?