From Certified Problem Solver El Gato comes this re-use for your old hub shells & disc rotors...
1. Find an old hub with 6-bolt or center lock disc mount, (ideally with a larger hub shell)
2. Locate a used rotor; pick your size
3. Use the proper hardware to mount rotor to hub. Bend outer edge of rotor downward, to "lift" the center of the rotor upward, making room for bolt heads. Avoids wobble. Takes a little time but works out well.
4. Clean it up, make it shiny
5. Insert a "plug" at the bottom (I used foam) to stop the pens from falling through
6. Place pens inside, and enjoy the envy of your peers