The Jasper Dairy access site to the St. Joseph River is in a very secluded spot compared to most access sites. Just follow the signs as the road turns from paved to gravel. The park is about a mile east of Highway M-139.
Note that the last portion of this road is not likely to be plowed in the winter, so travel at your own risk if there is significant snow.
You are looking for a magnetic nano bison, hiding in plain sight.