There is a frame called the "Cooper" it is between a youth and a standard sized frame.. Only problem with it, it is fatter and square in the back.. It is available through the supplier that most everyone uses for frames. .
Problem lies in the fact that nobody to my knowledge stretches a cooper frame for sale purposes..
Somebody may be willing to stretch you some in a cooper, but the problem lies in the fact that not everything that works in one frame can be applied to the next frame and thus the R&D cost for the call builder can be high.