Stir plate modification

My stir plate has been working well, except for when I try to do a 2 quart starter. It's a little too much for the stir bar and magnet, if I try to turn up the speed, the stir bar falls off. So I moved the magnet closer by cutting a hole in the top and building up the height with some double sided sticky tape. Now there is much better bonding between the magnet and the stir bar, and no trouble turning the speed all the way up.

The box itself is pretty straightforward:

Box: https://www.amazon.com/gp/product/B005T7AMUW
Switch: https://www.radioshack.com/products/spst-12v-dc-illuminated-switch-3
Speed knob: https://www.radioshack.com/products/radioshack-control-knob
Speed control: https://www.radioshack.com/products/radioshack-25-ohm-3-watt-rheostat
Power connector: https://www.radioshack.com/products/radioshack-size-m-panel-mount-coaxial-power-jack-w-switch

Total is about $25, with the box being the most expensive part at $20. There are cheaper boxes available now that would be sufficient.

Stuff I had laying around:
computer fan
magnet from an old hard drive
5V wall wart