I play in a vintage league which wears 1800's style uni's. Baggy Wool authentic looking jerseys. I'm sure you could contact the people who make these types of uniforms and see if anybody makes a child size uniform. I imagine this won't be the cheapest or quickest way to go though and given your time and budget may not be an option.
Would look cool though...
www.simsburytaveneers.com
The link above has some great photos of the uniforms the teams in our area wear.