A big bottle cage from TwoFish. For 4" diameter (10cm) camping bottles. Coated with black grippy vinyl dip.
Has three mounting tabs but will go on your bike even if it only has the usual two bottle braze-ons. But if you mount it this way you prob shouldn't put a huge heavy monster bottle in there.
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.