Jared: There are many outfits still engaged in spraying.
I suggest you browse a couple of the spray company websites to gain some basic information and then contact one or two of them with your enquiry. They will immediately ask what type of crop you have, what it is you want to apply and the size and basic layout of the area involved.
Here are a couple you can start with:
Apex Helicopter Inc - Home
Home | Applebee Aviation
Helicopter Air Services
Welcome to Lohman Helicopter
http://www.sintonhelicopters.com/
You can also try:
National Agricultural Aviation Association
I think you will find that any of these people will be willing to speak with you and provide basic information and if you can find an operator near your farm they may even come over and discuss your requirement.