I moved from Hammond 6 years ago. When I fished Pine Lake in Baldwin, I would get bait at the convenience store (Cenex maybe?) at the intersection of US 63, State 64 and State 46. It's 8-10 miles north of Baldwin. It used to have a good selection of live bait, minnows, some fishing supplies, etc. I haven't been in there in a few years, though.
If I was going to fish the lakes in Polk County, I would stop in Amery at one of the bait shops there. There's a very nice bait shop just north of Amery on 46, but I can't remember the name off the top of my head. There was also Apple River Sports at the intersection of US 8 and 46, but I heard that they had closed down.