Well, I've been doing this for a long time and approach it from commercial experience, but if you do it with a wooden or fiberglass boom it really can be an afternoon project as simple as using and eight foot length of 1x3 (edge "up") for the boom, attaching the elements across it with a couple screws on one side and stapling your feed line to the opposite side of the boom. Toughest challenge there is a good way to attach the boom to your mast or tower since it is heavier and the torque greater, both in holding it up and dealing with the wind, but you can certainly run a brace up to the back of the reflector element from below, and the further the reflector is from the mast the better. IF you're really lucky you have a tree or a properly oriented second floor corner of the house you can screw it to.
If you do use wood AND don't want to bother with a BALUN I would recommend wrapping a coil of about ten to fifteen turns of your coax around a 3/4" dowel right before the feed.
I could build you a kit I suppose, but it would probably be too expensive in light of all the cheap "ham consumer" alternatives out there. Maybe if there was a need for a dozen or so it might be worth considering since scaling would definitely bring the costs and time down significantly. I put that design out there for the benefit of our little community and wasn't really thinking about it as a commercial opportunity... but if anybody else does that's fine with me, I'll sue them if they are successful