A couple of years ago I built a boom sprayer for my 4 wheeler mounted 15 gallon tank with pumpI already had. Just go to a farm supply store and get 5 or 6 fan spray nozzels and a few feet of rubber line. Take a short piece of angle iron or something similar, get your spacings laid out, drill holes for the nozzels and put it together. Should be able to build one for less than $20. It doesn't take long to spray an acre plot with the one I built.