Hey, Check out the MN DNR webpage and search for trout streams. You'll get maps for the the southern part of the state that should help you close in on some streams. http://www.dnr.state.mn.us/fishing/trout_streams/index.html
I'm not real familiar with that area but you could call the guys at The Fly Angler, http://mnflyangler.com/ or Cabelas in Owatonna and ask for the fly department. Either one would be a good resource and could recommend some flies and streams. I would pick up your flies in CO since The Fly Angler and Cabelas would both be a decent drive from Mankato.
Where are you at in CO? I lived in Loveland for a few years and used St Peters fly shop in Ft Collins. Great place.
If nothing else you could try the smallmouth fishing on the Cannon River east out of Northfield. Good luck. Matt