I brewed up an extract wit once or twice and it came out pretty good! One of my favorite beers to brew and drink.
The recipe I used, off the to of my head was:
50% extra light extract
50% light wheat extract
1 ounce East Kent Goldings hops. (60 minutes)
.75 ounce coriander (Add at 5 minutes or flameout)
.75 ounce fresh orange zest (not the bitter white stuff underneath)(add at 5 minutes or flameout)
Clean ale yeast like Nottingham for Blue Moon type beer
Liquid Wit Yeast for true Belgian character (funkiness...)
Granted, this is all off the top of my head. I think it was 3 lb. bags of extract, one each of malt and wheat. The amount of orange and coriander you use is a personal preference. I'd go up to 1 ounce of each myself, but that may be a bit more than you like.
You could also use dried, bitter orange peel from the store. Many people do, but I've always used fresh zest. I've even used a bit of lemon peel as well. Feel free to play around and see what strikes your fancy.
Rumour has it that Pierre Celis used to put Chamomile in his recipe.