Are you asking about what's available interstate? You'll still have to have a Michigan dealer do the ultimate transfer of the SBR to you (on a Form 4) so you may just want to wait and see what your local stores will be offering.
Or, if you're just wanting a SBR AR-type rifle, you can register your pre-existing AR (assuming that you have a pre-existing AR) on a Form 1. When the approved form is returned to you, you can acquire and install the short-barreled upper of your choice.
Either route entails a looooooooooooonnnnnnnnnnng wait time.