this is what I currently use, from west marine. I would mount it to the top of my canopy but the rail mount base won't stow properly. They also make an adjustable light pole mount from cabelas that adjusts 26" to 46" that I'm considering to put in the bow light plug in.
Developed with the Pontoon Boater in mind, this new injection molded, black nylon mount attaches easily to the top of your pontoon railing and features a 10 degree presentation angle. The 3/4" diameter bright dipped anodized aluminum pole simply snaps into the base and features color matched...
i tried these for a couple years but in the run a boat eventually they would snap at the base due to the speed. thus loosing my flag and the pole. i'd also leave them on during tow. they made it to powell one year but lost my colorado flag last year with these. I tow from Denver.
i looked again this year forever. i like mounting them to my bimini top so they are up and out of the way. i bought 2 of these this year thinking no way these would hold up either but i've been out on the water 45 days this year with them 9 days on powell and towed back and forth to denver with no problems (flags are stowed while towing of course.) i just put 2 small carabiners on each key chain loop for easy on and off of the flags.