I liked the USB flash drive cryptex (http://www.thingiverse.com/thing:1196989) but wanted to be able to change the combination, I got the idea to use a two part combination ring from this (http://www.thingiverse.com/thing:830293). The cap can be removed when the device is unlocked which then allows the rings to be removed, the combination changed, and then reassembled.

The flash drive case customizer from (http://www.thingiverse.com/thing:1740723) was modified for the increased length of the cryptex due to the addition of the locking cap and addition of some friction fittings so no glue is needed.