So, is the experiment to see how often once in a blue moon is? Or are you just looking for eggs and hoping they'll hatch. 
If it's the first one, post your results as I'd be interested to follow along! If you're just looking to hatch, there are lots of folks in RI who sell fertile eggs (especially around the Foster area, where I've bought from 4-5 different people). 
But to contribute to your original question....in RI we have the big 3 groceries of Stop & Shop, Shaws, and Dave's...there's Whole Foods, Roch's, and there's a small place near me called Tom's (Rt. 3 Coventry). Not sure where any of them get their eggs....but they're smaller than the big guys.
Good luck!