A big bottle cage from TwoFish. For 4" diameter (10cm) camping bottles. Coated with black grippy vinyl dip.
A couple wide and strong velcro straps for straping it on almost anywhere on your bikepacking rig.
Robert of TwoFish has made clever things since 1993, always in the U.S., and it's been a good life. They work as intended and come in handy for other things, which you can discover yourself. The entire country of Japan is nuts over the flashlight holder-if I told you how many they bought a year you'd think I was lying. The actual figure is confidential.