ISO/WTB: 50-53cm 'cross frame for junior

We've got $200 to spend on getting as much 'cross bike for the buck for a junior racer friend of mine. This means, if you've got a fork and headset you'd throw in or trade for something else, that would be cool too.

We're looking for something in the 50-53cm range. Any material is fine.

Thanks!

-will, Word-RCB