Dinny,
Al & Bob's Sports, Rylee's Ace Hardware, or for a drive Bob's Gun and Tackle in Hastings or Wilderness Dreams in Sand Lake.
I don't live there anymore (moved to God's country - the U.P.) a few years ago so don't know what they have, just likely spots to try. If you live there I'm sure you already tried all or most of them.
You might go on the Michigan Gun Owners forums and check around. Might find some for sale by a member or a tip about where to buy some.