I bought a Cricut Maker. I now have magnet numbers. I recreated the font from the car numbers in MF Ghost.

Magnet numbers how-to.
You will need a Cricut Maker (the $400 one), magnet vinyl (available from Michael’s and/or Amazon), software that can output .jpgs or .pngs, and the Cricut app. You can add colored vinyl to laminate with for an extra challenge.
1. Prepare the magnet vinyl by magnetting it to your washing machine, fridge, steel door, or any other flat surface. It comes in rolls and needs to be flat to go through the Cricut nicely. Leave it there for two days. If you are laminating vinyl on, then unroll the vinyl and hang that up to flatten, too.
2. Design your numbers. Use your graphics software or whatever. Output a graphics file that the Cricut app can read (.jpg seems to work better than .png).
3. If you are so inclined and really want hot pink numbers, laminate the colored vinyl to the magnet vinyl. This is not easy and it took me to the third go before I could make it look decent without a million bubbles. Don’t hate yourself.
4. Load up the Cricut app and set your design. I found that using the whole 12×24 sheet of magnet vinyl on the 12×24 grip pad worked better, but then you have to drop the $$ on the big pad.
5. Stick the magnet vinyl to the grip pad. Make sure it is exactly in the lines because the positioning rollers will push it around if you are running the full 12″ width sheet. This will cause cuts within 0.5″ of the edges to not be just so.
6. Set the material to 0.5mm magnet sheet. 0.6mm also works, but tends to cut through and into the grip pad. DAMHIK.
7. Cut your numbers. At 0.5mm it will run the pattern twice. This is normal. I think it does three times for 0.6mm.
8. Put your numbers on your car and look awesome at the track/autocross.
I have been running this material for several track days now, and have left them on by accident (lol) for driving to work (lots of traffic and highway). It stays on well and doesn’t move around. Do make sure your car is very clean before sticking the numbers on as if there is dust, it will get into the paint.