Hen Savers or krazy k farms (same comapny.) I bought 4 from them and they are VERY well made and my girls have been wearing them for over a month now and their feathers are growing back just fine. Definetly get the double strap kind otherwise they will be able to get them off rather easily. If you pay an extra $2 for shiiping you can have them in 2 days.
Be prepared for the hens to act like they are being killed and the rooster will most likely attack the approns at first, because it looks like a predator has them the way the hens flop arround and scream. I put them on at night (which did not help the circus any), but they were both running around when I got home just fine. Also be prepared to feel like a complete jerk for putting them on in the first place since they will give you a dirty look for at least a couple of hours.
As far as fit goes I have a rather small easter egger and the large fits her just fine and I have a slightly bigger girl of bubious decent and the extra large is way to big and the large just barely fits. You'll have to work the fit a bit to make sure they do not pop up when they bend over, but once they are adjusted correctly they are fine.
Can't say enough good things about the Hen Savers.