Now that MN allows an added line w/hook, I just use a sucker or shiner rigged to a hook and a red and white golf ball on a spinner. I have used decoys before and sucker harnesses. I don't like the added weight of the harness. Last time I went I never had a northern grab the minnow, they'd come in slowly and stare at it or the golf ball.
Fleet Farm used to sell the Nils ice saw, which I picked up more than a decade ago - not sure if they still make them though. I hear good things about the Fish's saw.
I don't think you can get a bad spear, IMO. Back in the 90's I picked one up at Fleet Farm and I believe they're much better now. I bought a Clam spear several years ago, which has a wooden handle, but haven't used it because I continue to use one of my cheaper ones.