I bought a 12v plug (c/w the USB 5v plug at NO extra cost!) from Cycle Gear last winter, on sale at about $10, and installed it yesterday. Here are pics of what product it is.
Once I had removed the factory plug
I checked the size of the hole in the dash
which is the SAME size as the Cycle Gear 12v adapter
Once I had 'trial-fitted' it, I removed it and looked for a couple of 'bullet-connectors' in my electrical stash, and found one each, F and M.
Then I looked at the wires beside the Kawi relay I'd installed for about $16 Cdn last year, and checked for 12v w/ a multi-meter. YES - ignition ON - 12v, OFF - NO v...!
So I removed enough of the electricians tape to free both wires,
cut about 28" from the Cycle Gear adaptor pig-tale, then crimped the two bullet connectors on (female onto black, male onto red), followed by soldering, then 'shrink-wrapping' them,
installed the plug thru the hole in the dash (I'd picked the left-side one because of some members reporting clearance issues when using the right-side hole)
then attached the two bullet connectors (also a bit of electricians tape DESPITE the shrink-wrap)
checked for voltage (zero), then ignition ON, checked again - 12V!
and here it is - COMPLETE.
Took maybe an hour, not counting removing the windscreen and 'meter-cover', and works my 12v compressor. Not bad for $10 and some time....