Does anybody know where I can find a "Le Petit Prince" Halloween costume?

You mean from the book, "The Little Prince"? Any children's prince/renaissance costume should work, as long as you aim for 16th - 17th century fashions. No armor - fashion instead would have been tall riding boots or soft suede ankle boots, tights, doublet with long, "poofy" sleeve shirt, rapier and dagger - no "hack and slash" swords, and use rich, sumptous looking fabrics.

In the SCA, or Society for Creative Anachronism, you (NE Ohio) are in the Midrealm, an SCA Kingdom. Try looking up Midrealm on a search, and using their page find and email your local SCA group. Odds are high someone there can help you, or knows someone that can. Most of us have enough knowledge of our chosen time period to teach a college level history class. (and some of us do.)

im so sorry but i goggled and yahooed it nothing is coming up try and make it sorry good luck.