Buy a copy of Uncle Henry's. There are a number of older chicks and some laying hens for sale in there. Part of the fun is starting from day old chicks so I suggest you really consider doing that. My first 5 chicks last spring were 2RIs, 1 Austrolorp, 1Buff Orp, and 1 Easter Egger plus a RI Cockerel. I bought 4 more RI chicks the last week of August. Merging the two groups happened wasn't easy but they became 1 flock in the winter.
You are in for a real treat.