Check your
local feed store bulletin boards, or put one up yourself. If you have a local Nickel classified paper, check there.
You might also consider just hiring someone to do it until you find what you want (they can be an expensive mistake, as a friend discovered). And there are guys who do custom plowing, too, if there is access to your growing area. Call places that repair lawnmowers and tillers (if they repair one, they probably repair both), so see if they can give you a lead on who might be willing to help out, esp in the off-season.
Sue