I used gray carpet runner from Home Depot... I think it was $4 worth.
Then to lighten things up even more - because the inside of black saddlebags are like a cave, especially in a garage - I picked up a couple of those LED switch plate lights.
I paid $5 each at Harbor Freight, but you can find them all over for $2 on sale. Forget about the mounting magnets, and forget about the enclosed imitation velcro and the OEM AA batteries.
Get real batteries, and the really high quality 3M clear plastic hook and loop fasteners rated for 10lbs, then mount the lights inside, on the angled top backs of the bags.
WOW thassa lotta light inside! No more searching in the dark.