Here are the ones that I am aware of. Not sure if you have tried these already. Hope this helps.
ELEMENT ARMS
BIG LAKE, MN
MINNESOTA FIREARMS TRAINING LLC
ANOKA, MN
TOTAL DEFENSE INC
RAMSEY, MN
BLOK TACTICAL LLC
EDEN PRARIE, MN
ARNZEN ARMS LLC
EDEN PRARIE, MN
ATOMIC TACTICAL INC
BLOOMINGTON, MN
LIGHT'EM UP GUNSMITHING LLC
MADISON , MN
EVERLASTING ARMS
GILBERT, MN