I am an insurance agent in West Virginia. I have my insurance with Farm family, and they are great. Like someone else said, check them out if they are in WI. Not all BIG insurance Companies provide farm coverage, but there are several small companies that specialize in farm coverage. You can contact your local extension agent or your local farm bureau and possibly get some assistance. You can also contact your state Insurance Commission for a possible list of farm policy providers in your state.
If you need any assistance or want some opinions I would gladly help you as much as I can.
What ever you do I suggest that you stay away from ERIE Insurance. They are the worst!!