Baltogs makes a full bottom dance belt, and is one of the few available in both men's and boy's sizes. However, the full bottom also means you'll have visible underwear lines if you wear tights.
Thong style dance belts offer the best support, no visible lines, and don't interfere with your gluteus muscles. If you ever perform in white tights, you'll be required to wear one, so you might as well get used to the feel. The doctor would prescribe trying different brands of thongs before going with a full bottom. Thong style dance belts do take some getting used to, because by definition, they give you a wedgie.
If you've given thongs an honest try, and really can't handle them, you might consider a modified thong such as the Capezio "comfort" model. The rear is wider than a thong, but narrower than a full bottom. It still rests in the gap between your cheeks, so isn't as visually obnoxious as a full bottom. [/i]