You could always try this "Cyalume holder", about $2 on fleabay... I use them as pen holders in my Maxpedition bags
https://ae01.alicdn.com/kf/HTB1LKdERF###XcjXVXXq6xXF###O/2pcs-lot-Cyalume-Chemlights-LiPo-Batteries-Patch-Pouch-Military-Attachable-2-CR123A-Surefire-Batteries-Stiky-Holder.jpg_120x120.jpg
** EDIT **
Tried them with some 308, you'd need to had some stitching to make them tighter.