As a retainer for my inflator, I use length of 1/8th inch bungee cord tied into a loop using double fisherman's knots. This is retained by a tri-glide/belt stop along with a D-ring on my left shoulder straps.
For lights, I cut rings from a mountain bike inner tube and cut a slit in them about half way around, I use these as retainers to hold bungee loops in position on my shoulder straps. The bungee loops act as keepers for the torches and make it possible to reposition the keeper along the length of the shoulder strap as desired.
Because it is a hassle to unthread/rethread the harness webbing through the buckle, d-ring/slides just to replace one of the inner tube rings, I have a couple of extra pieces of inner tube slid on my shoulder straps as a ready replacement should one of the ones is use break, which is rare.
I think the EPDM bands are a slightly cleaner look but they are more expensive as a popped inner tube can be obtained free from a local bike shop.
My recommendation is to put a couple of each, inner tube/epdm/o-ring/bungee on each shoulder strap of your harness and test each for which one works better for you. None of the options are very expensive, unused they will be unobtrusive, and when you decide which style you want to use you can just cut off the others.
-Z