I have been running a MSR bottle for spare fuel for awhile. I haven't needed it myself yet, but I have helped at least two folks on the side of the road with it. The child proof caps are tricky to get on good and get off. I helped a kid near St Louis on sporty that didn't know how to operate his petcock. He was riding with a guy on a bagger of some sort and I assume it was his dad. The older gentlemen really wanted give me $10 for the 30 ounces of gas. I didn't take it of course. When I refilled the bottle at my next fuel stop I forgot to muscle the cap on good and immediately lost it on the road somewhere. Sadly this is the second time I have done this luckily the first time was in my neighborhood and found the cap. At any rate a replacement costs about $10 delivered, while a whole new bottle is only $20. I'm sure this is why a motorcycle specific caddy has a strap across the cap. Anyhow I'm cheap and this is my solution to my next potential lazy spell. I should have taken that guy's money, too. HA!
Zip tie with a mounting hole.
Put that on the bottle neck.
Put a hole in the new cap.
A little paracord and two stopper knots. I don't think even I can lose this again.