There is a member on Purrs who makes cat posts and sells them for their rescue, sorry but I can't remember who it is now but I'm sure someone will be along to tell you and show you the pictures. There's also tutorials online on how to make your own, all you'd need is some offcuts of wood, sisal rope and fleecy fabric for covering, as well as nails etc. I imagine it would be pretty easy to do one youself, and you could make it elaborate as you wanted