It's likely that investor-friendly Realtors participate in some of the real estate investment clubs around Green Bay. Here's a link to Wisconsin clubs: http://www.creonline.com/real-estate-clubs/wi.html
I'm puzzled at some of the of the other advice below:
"an experienced agent who has an extensive knowledge of construction" I just don't get that one at all. There's no assurance that an agent with "extensive knowledge of construction" knows anything about investing, much less that that agent is investor-friendly.
And while I'd agree that experience is preferable to little/no experience, watch out for agents whose extensive experience has been with typical, traditional real estate.
Here are a few questions to ask any Realtor you're considering:
(1) How many investment properties do you own?
(2) Tell me about the last three clients you had who were investors. What were they looking for and how did you help them?
(3) Can you give me the names of some references who are real estate investors?
(4) How do you feel about land contracts or lease options? [An investor-friendly agent will at least be open to them; if the agent says they're not good or they don't work out, move on.]
(5) Do you know any hard money lenders? Who are they? [In many cases, you wouldn't want to use a hard money lender. But an investor-friendly agent should know of some.]
(6) Is it possible to be a real estate investor without buying or selling real estate? If so, can you tell me a few ways? [Sandwich lease-options and wholesaling are two. Or using straight options. Buying and selling notes would also be an acceptable answer.]
If the agent can't answer most of those questions, then the agent isn't investor-friendly and/or the agent knows almost nothing about real estate investing.
Hope that helps.