I haven't ever fished near Le Mars so I can't help you with anything very close but I do know one good place to the north.
Lake Pahoja in Lyon county is a pretty good fly fishing lake. It's a little early in the spring for the crappies(the most caught fish in the lake) to really get going but with the warm weather it might be worth a try. Last time I was there the bluegills were a little small but very plentiful. Good population of LM bass in there and the rare but occasional northern pike to spice things up. I haven't caught a catfish on a fly yet but this is one lake it wouldn't surprise me in.

I haven't fished in IA for a couple years(but did for nearly 20 years before that) so I can't give you any up to date info, but if you are going to give it a try I can email you a map with a few places to try.