Ammunition Depot has the hard to find Federal Premium LE Tactical® #1 Buckshot 12 Ga 2-3/4". Looks like they have plenty.
http://www.ammunitiondepot.com/Federal-Premium-LE-Tactical-12-Ga-00-Buckshot-p/le1321b-a.htm
http://www.ammunitiondepot.com/Federal-Premium-LE-Tactical-12-Ga-00-Buckshot-p/le1321b-a.htm