The FoldIt cart is what comes to mind but it might be more than what you’re looking since you’re looking for a single tank.
I use it for ferrying everything back and forth from parking to the boat in one shot. It’s large enough to accommodate you and a dive buddy with two bottles each plus your deck boxes.
EDIT: Handles stairs without a problem.
I also use it to carry my twinset, my two deco bottles, my deck box and a DPV.
It serves double duty for carrying motorcycle wheels back and forth to the tire changer at race tracks, which is where I first learned about the FoldIt cart.
I’d check online with your home improvement warehouse for foldable hand carts. There are some slick ones I was considering before I splurged for the FoldIt cart.