The list a few posts up is pretty good. DK Mags in New Brighton is one I'd add to the list. Its been a while since I've gone browsing in a gun store, so I don't have a good sense of who has what in stock anymore.
Since you said you're heading up to Alexandria later, it might be worth it to stop by Alex Pro Firearms. They're about 10 miles north of Alexandria. Their storefront is pretty barebones, but it seems like every time I go there there are some hidden gems (usually AR parts).
I stopped going to Frontiersman when the owner came out in favor of some proposed gun regulation. At least that's the way I remember it, I could be wrong.
There is a store in Lakeville that used to be called J&S Custom guns. I think it's Dakota Custom Guns now. Most of their stuff is on the wall behind the counters and is barely organized. Reviews on that place are....mixed.
If you're only going to one Bill's location, I'd recommend the Circle Pines location. I just see more sketchy customers at the Robbinsdale location. I hear that there is a Bill's across the river in Hudson as well, but I've never been to that one.
ETA: I stopped by Modern Sportsman in Burnsville today. Inventory is still good.