A little follow-up on this thread, here is what I ended up doing.
Not the fanciest looking setup with the duct-tape but it gets the job done quite well using materials I had sitting there in my shop. It turned out my parents had a bunch of old MSR bottles, so I used two of those that look very different to make the gas/oil bottles obvious. The gaskets were cracked, so I had to buy new caps and gaskets, and since I wanted leashes on the caps so they couldn't be dropped, the swivels were necessary, a few bucks at the hardware store.
Overall it's a very durable setup that I'm happy with so far. Using the para-cord loops and carabiner to hang them on my saddle is far more comfortable than hanging them from their own caps. Even if I don't need to refuel in a tree, on the jobs where I do multiple removals back-to-back, just having that on my saddle means it's there when I come down to refuel between trees, I don't need to head back over to the truck for the big/primary gas and oil.
View attachment 74147
View attachment 74148
View attachment 74149