I ran out of welding gas and as I was headed out to get a refill, I realized that I did not have a safe way to transport the full bottles, so I made some bottle holders that mount on the side of my trailer out of some scrap plywood and 2X4s. After I used them for the first time I painted with HiVis orange so I would not lose, runner, or toss them. Side note, when you are hauling use more than 1 strap and/or use a chain attached to a static point with a a lock link.
Be REALLY safe with gas bottles!