In Lansing, the Michigan Historical Museum has a large Michigan-themed gift shop, and the periodical Michigan History magazine (http://www.michigan.gov/hal/0,1607,7-160-18835_18888---,00.html) offers a wide range of products.
Visit the History e-store on-line (http://mi-mall.michigan.gov/webapp/wcs/stores/servlet/StoreCatalogDisplay?storeId=10151&langId=-1&catalogId=10151).
Merchandise featuring the Travel Michigan Great Lakes. Great Times. lighthouse logo can be ordered on-line (http://www.mic-store.com/trmigrlatige.html).
Visit one of the 13 Michigan Welcome Centers (http://travel.michigan.org/industry/welcome_centers.asp) to pick up a catalog. The Mackinac State Historic Parks has gift shops at each site with great publications online (http://www.mackinacparks.com/books.shtml).
For more great Michigan gifts you can also shop the DNR e-store online (http://mi-mall.michigan.gov/webapp/wcs/stores/servlet/StoreCatalogDisplay?langId=-1&catalogId=10051&storeId=10101&orderId=null).