Here are two more ideas from the Pico thread (with links):
One is mine.
The other is courtsey of get.lit.up
Here are some ideas that I had and posted in the Pico thread:
I do think that if you could change certain parts of the design it would be possible to downsize it
I've been looking at mine as well as reading up on other people's ideas (as I'm sure you have been) and I've come up with a few things.
1. No electronics/use clock spring only (not possible with all Halos since some Halo-A models don't have the spring)
2. Do away with battery door and board area.
3. Integrate the catch cup into the shell; as per Pump Scout (I think) on PBN.
4. As catch cup is designed into the shell the motor (as per 1) can be done away with.
If electronics are kept you could still do number 3 although the size savings would be minimal.
An option would be to design an arduino controller or similar small board to run the electronics and perhaps change the voltage required to operate (thus changing the size slightly).
Yet another option would be to do away with the board (for the most part) and rig up a small board that just uses a microphone as a switch ala the Reloader B. Keep it crazy simple and have the motor spin only when the microphone is activated by firing the marker.
If a lower voltage input can be used with the board (not 100% sure if it could but you really only need to feed 12.5; less with a pump) then smaller li-poly batteries could be used.
Here are a few:
Lithium Ion Polymer Battery - 3.7v 1300mAh -
Weight: 25g
Size: 1.35" x 2.55" x 0.23" (35mm x 65mm x 5.5mm)
Output: 1300mAh at 3.7V nominal
and
Lithium Ion Polymer Battery - 3.7v 2600mAh -
Weight: 52g
Size: 2" x 2.55" x 0.30" (51mm x 65mm x 8mm)
Output: 2600mAh at 3.7V nominal
That could change the size because it would allow battery relocation nearer to the board as shown in the Magna picture.