Herters from Cabelas is what I've been using.
http://www.cabelas.com/product/Herte...se/1545677.uts
Wait for one of their $5 flat rate shipping and get a couple cases. Way cheaper than dicks. Also just ammoseek.com. Trick is to find somewhere w/ a free/low-flate-rate ship deal and buy a bunch at once. I've been able to buy a couple cases around $5/bx shipped if you time the sales correctly. Black Fri sales are coming up!
http://ammoseek.com/ammo/12-gauge