As of 2:40pm today, 7.62 ammo was still available online at several dealers. Just wanted to pass it along since I have spent all morning tracking some down.
The following websites all had several options available at decent prices. They may change by the time you read this but as of 2:40pm on Jan 2, 2013, these websites all had a decent selection.
J&G Sales (Only 1 option but decently priced)
Cheaper Than Dirt (Several options were available)
Ammo For Sale (There were 3 or 4 options)
Ammo.net (3 or 4 options)
Bulk Ammo (3 or 4 options)
Lucky Gunner (3 options)
Pretty sure most of these websites are all getting their stuff from the same place, so It’s possible they could all run out at the same time as well. I bought some while I could and you should too. Happy hunting and good luck!