Dick's Sporting Goods or on their online store .... They sell a "Magnum " double ladder stand I think made by "Field & Stream". These stands are huge. They have big full platforms that can hold your pack or anything else on them. They also have a couple of storage packs (small, one on each side) and an adjustable padded shooting rail, padded seats w/ warmer pockets.
I put one of these together and installed it for a friend of mine and was impressed with its overall appearance and functionality. If I had a place to put one, I would have bought one myself.
You will need a decent size tree to put this on. The stand is big & heavy and needs a larger diameter tree for full stability.