i think a lot depends on how handy you might be: i have seen parts at local farm stores (here in western oregon) for repairing spray tanks that, taken together and throw in some hoses and little plastic fittings should give you a handy tank spray rig. my neighbor did that, and then mounted it on an old push lawn mower body (sans engine and blades) for toting around his small orchard (similar to your size).

falkenburg is a local oregon brand we use, but i wonder that the farming communities (maybe even the amish? what are they spraying with?) of PA don't support a sprayer manufacturer. i'd poke around on the net, and maybe ask some folks at a rural farm store/hardware store for their ideas.

good luck! oh, and ask at somewhere like a john deere lawn tractor/mower dealership. i don't think they offer one (at least not cheaply) but they might have an idea of local makers too....