McCormick, I think they're called, the guys that always have the huge spice display in grocery stores, has orange peel. It's easy to find, here in my neck of the woods, anyway. We just did a Wit with it.
Primary- Pale Ale
Conditioning- Belgian Strong Ale
On Deck- more Belgian stuff, Cru
Drinking- Weizen, Wit, IPA, Tripel
It wouldn't be an exact match, but you can just dry out some Tangerine peel, or some other thin skinned orange-type citrus. For orange flavor it'll come close enough in a pinch.
You don't get the orangy flavor of a wit from the orange peel ... that comes from the corriander that's added. Orange peel most oftenly gives a bitter-spiciness to beer with an ever-so-slight citrus flavor.
I've used dried tangerine and orange rinds before. You could probably just get some oranges, peel them and dry the rhines in the over for several hours.