I recently started using the 5 round leather ammo carriers that fit on my belt. I wet the leather and insert the desired cartridges for that carrier and let it dry. While drying the leather will form a perfect snug fit for your ammo.
Been using this for two years now and haven't lost a single cartridge to date. My last trip was spent running around South Africa for 14 days. Makes it easy to retrieve a round, or two, when needing to reload.
I carry addition rounds in my pack to replenish those I've used on my belt.
Good luck!