Off the top of my head, and based mostly on squinting at the above linked map, here's a probably not comprehensive list of the businesses that I have personally patronized or otherwise had a direct interaction with in the past 5 years that are located within District 3:

- Federal Pipe & Supply
- J Fons Company [[a.k.a. The Dump)
- Marcus Hamburgers
- Buddy's Pizza
- Sikora Metals
- General Hardwood
- Spectrum Neon
- Great Lakes Power & Equipment
- Public Lumber

I'm pretty sure District 3 also includes the whole nor-ham/powerhouse neighborhood.