I’ve read a lot about fireworks safety!

I don't know what their hours are, of if they're even open this time of year, but there's a dominating fireworks shop in Bad River, WI.

Illinois day-trip.  It'll be worth it.  Trust me.

A neighbor of ours sometimes goes to Victory Fireworks in Danbury, WI.  He has brought back some pretty entertaining stuff from there.

North (or South?) Dakota. It's like they've got no laws.

Also, I wouldn't be surprised if Target already has those packs of things that sparkle and/or pop.

If you're looking for safe fireworks (that don't go up), they can be found around most of Minnesota a few weeks before July.
If you're looking something bigger, I'd also suggest Victory Fireworks (rumor has it the bigger stuff can be found in the central Wisconsin stores that aren't near the border).
As long as you are are using commercial fireworks and your common sense, you will be perfectly safe. Many firework accidents are the results of stupidity with commercial or homemade fireworks (ie: don't mix your own and then hold it in your hand).

South Dakota has fireworks laws. If I recall correctly it is something like South Dakota residents can only buy fireworks for a few weeks around July 4th. If you are a resident of a neighboring state you can buy fireworks any time of the year. Nevermind that one's home state bans exploding (firecrackers) or rocket type fireworks.

I know people who set up a stand in the Miller Hill Mall during the 4th of July and will send this link to them and they (I'm sure) will contact you.

What's your address?  I'll overnight some to you via Fedex.