500grains & Alan:
Here's a couple of photos as requested:

Cartridge wallet closed:

Cartridge wallet open:

Don't get too concerned about the elaborate flap, the unit has seen many mango-seasons and its simply a press-stud repair which will never break again!

This design could easily incorporate stitched pockets for each cartridge, and a peg rather than a press-stud for the ligyrophobes.

I wear it right at the front like a spurren, so it can be dropped open and cartridges retrieved without taking my eyes off the quarry.