Shift boot bracket for e46. This is the part that glues down to the shifter boot bottom.
Should work for M3. You may need to check these dimensions or sand down a bit, I haven't had time to test yet. I'll update this when I test it.
Just test fit this in HIPS and ABS. It is a little tight with Alcantara. You may want to print it at 96% scale or so to get material to fit better.