Thanks to Flomaster and his thread
I picked up a Thermatake USB desk fan from Amazon
It's a 3" fan with a retracting USB power cord and a speed control.
The first thing I did was take it apart. Removed the 4 screws and the little stand. I moved the screws around to serve as legs & swapped sides with the fan guards.
I took the guard with the Thermatake logo and cut the center out by clipping the 4 wires. In retrospect, I wish I had used the other guard instead as it would have allowed the magnet to be a little closer to the flask as it is offset less, not that it mattered. Just a minor detail.
Next I scrounged a fender washer from the junk box, I peeled the label off the fan hub, cleaned the hub & washer with solvent and set the washer in place. I gently spun the fan with my finger and eyeballed the washer to center it. It didn't take long nudging and spinning to get it where it was centered with no visible runout. At that point I dropped some super glue into the center of the washer and let it set.
The washer is important to shield the motor from the effects of the strong magnet. If you don't use a washer, then you need to space the magnet(s) some distance away to prevent them from interacting with the magnetic field of the motor.
While the glue was setting, I tore apart a 3-1/2" HDD to rob the magnet from it. I could have used some spiffy disk magnets but I didn't have any and I'm cheap and wasn't about to spend $10 on magnets. I liberated the magnet from the HDD & cleaned the old adhesive from it.
I placed the magnet on the washer and used a 6" machinist scale to get it centered on one axis, I put the stir bar on the magnet and found it's neutral happy spot. I then nudged the magnet in the other axis until the stir bar was centered on the fan axis. All this was done by eye and by gently spinning the fan by hand.
Once I was satisfied with the magnet position, I put a bead of superglue around the magnet and let it set.
I scrounged a few 6-32 screws and attached the cut out fan guard to the top and that was it.
I used my iPhone wall charger, set the flask directly on the guard and away it went. I need to find some rubber feet/caps to go on the end of the screws to keep from scratching the counter, maybe some caps used for spare ports on aquarium air lines should work. It's a nice compact, easy to stow stir plate, my storage space is very limited. The 1L flask was from Stirstarters.com $12 delivered.
Here's it's chugging away with some washed US-05 in 800ml of DME
Thanks Flomaster and thanks Homebrewtalk!