Obviously state parks up in that area are a fall-back since they don't have FHUs. Here are some other options.
The City of Houghton has a nice little park on the canal in town, but there are only 22 FHU sites.
http://www.rvparkreviews.com/regions/michigan/houghtonRight across the canal in Hancock is another city RV park, but there is no sewer. The prices are cheaper though.
http://www.rvparkreviews.com/regions/michigan/hancock/hancock-city-parkOntonagon has a couple of parks besides the state park. We stayed at the Ontonagon Township Park, just on the north side of town and along Lake Superior, but again, no sewer, only water and electric. Never stayed at River Road RV Park, but it shows FHUs.
http://www.rvparkreviews.com/regions/michigan/ontonagonPhone numbers and web sites for some are available on those clickies I posted for you. Good luck. It's beautiful up there.