I bought a pair of black plastic storage boxes from Lowe's and bolted them to a hitch-mounted cargo rack. I think the whole thing cost about $150 and gave me 5' x 2' x 2' of additional storage space. That pretty much doubled my storage.
The empty weight is maybe 40 pounds, and since it's on a very long 2" x 2" hitch shank I just pushed it fully into the receiver and put the pin through ahead of the entire tube, not through the drilled hole.
If I need less capacity I can remove one and put other stuff on one side.
If you're concerned about weight, just use a good quality BBQ grill cover and fasten the chair directly on the cargo platform.
Ted 'n' Laurie, plus Jackson (aka Deputy Dog, the Parson Russell Terrier 'fur kid') and, Rylie (who crossed the Rainbow Bridge June 14, 2012).