I know this is an older post but, DSG has the best prices on 30rnd mags for the AR I have seen. I found the site after always getting outbid on older M7 bayonets on ebay. (30+ bucks is terriable for a used NAM era sticker. DSG has new issue M8's in tan, green, black for less so I picked me up one and 3 mags for my AR. They also shipped my order next day and thru in one of thier t-shirts.
Some things you cant get unless you are LEM or military contractor, but I bet if you called them and begged, you will get what you need.