Hey Jackie, if you are in Livonia, Zerbo's might have them. Have you been there? Also, if you can make the drive to Ferndale, the Natural Food Patch on 9 Mile carries only organic produce (along with other natural foods), and they have the best prices in town. I've been buying their organic grapefruit, have not priced the oranges as of yet, but I'm guessing they would be the cheapest organic in this area. The cost of their organic produce is on par with commercial. If you order a case of anything from them, they will give you a 5% discount on top of it. Their produce comes in Monday, Wed. & Fri., and I think the best day for citrus is Monday. Oranges keep a long time, so I don't see why you couldn't have them get a couple cases for you and just use them up as you go. Alternatively, I think commercial wouldn't be the worst thing. I don't think MH uses strictly organic.
Good luck on the fast. I'm hoping to give it a run, myself, sometime this Spring/Summer.