Mounting Storage ON TOP of RTT?

Some buddies and I are taking a trip out West in January, and because of gear needed for cold weather overlanding, we’re quickly realizing we don’t have nearly enough space. Does anybody know if there’d be a secure way to mount a basket or some other kind of storage on top of a RTT? It has the t-mount bracket spaces running down the side, but obviously I can’t find any racks to put on there. Any help is appreciated, thanks!