Not a "design" per se but there is a book, if you can find a copy, called "The Engineering and History of Rocket: a survey report" which is truly excellent and contains detailed drawings constructed from measurements made on the machine in the Science Museum. Plus a lot of background information. I feel sure you could construct a decent model of any of a number of the phases that Rocket went through during its development.
Even my 8 year old great nephew, during a brief sortie away from his iPod, pronounced it "so kewl" ….. high praise indeed!
Edit: I got mine from Camden, I think, but they don't seem to list it now so it may be out of print. Amazon UK list some "used, like new" copies starting at £12.45 with V2.80 shipping …. a real bargoon IMO
Edited By Sid Herbage on 31/12/2012 15:38:37