Like all the best ideas - simple and effective, and makes you think "why didn't I think of that?"
Thanks!. I have been mulling on the issue for a long time, considered buying the plastic glow-in-the-dark thingys that RM was selling, and then the proverbial ligthbulb went on over my head. Made three more today, two nicer ones for myself, and one for a mate. It is really quick once one has the measurements down: the key one is 4 cm between the two elastic pockets: then AAs will fit perfectly, and with AAAs there is a bit more room, but not so that it matters. I used 50 mm wide webbing, and matching elastic and velcro.
The workflow is simple:
1. Attack velcro loop patch by one end of webbing
2. Attach first pocket on the reverse side of the velcro.
3. Attach second pocket 4 cm away from the first
4. Divide pockets into two (quicker than doing it as the pockets are attached)
5. Add velcro hook part about 4 cm away from the bottom of the second pocket, Leave a short piece of free webbing after the velcro (0.5--1 cm).