I purchased TSC's 15 gallon pull behind tank sprayer. I mounted the booms in reverse so they are facing toward the front of the trailer when folded in order to store the unit in a much more confined area. It takes up much less linear space now.
It is a good little unit with one exception and that is the drain cap leaks. I put an o-ring inside the cap to try to eliminate the leak. It isn't a bad leak. However, if you need to leave the unit for a second spray in a few days, the tank will leak out.
There is one more thing I intend to try come spring and that is to draw file the end of the drain spout to see if I can make it flat enough to stop the leak in conjunction with the O-ring.
Mine can either broadcast spray or you can use the wand and drench their butts good.
I think you're on the right path with the TSC pull behind sprayer.
Good luck,
Max