Home Depot and most carpet shops will let you pick out carpet and have it bound to whatever size you want. We did this for a child's room, also. Don't forget to get some padding to put underneath, also.

We have 2 kids bedrooms that are wood floors. We'd like to carpet them so the kids can sit and play in their rooms and be comfortable, but we don't want to go to the trouble of getting wall to wall carpet and tacking it down. We'd like to just have a piece of carpet with the seamed edges to fill the entire room - anyone know of a place that does this? Or is there another idea I'm not thinking of?