Whatever Obama sold them in Benghazi taken from Ghaddafi.
Yep, a likely source.
“One unwelcome consequence of the war in Libya has been the escape from Libyan state custody of untold numbers of portable antiaircraft missiles, which have been carried off from storage bunkers as Col. Muammar el-Qaddafi’s military has ceded territory and military bases to opposition fighters. The missiles seen in the largest quantities have been the type visible in the photograph above, the SA-7, a Soviet-era weapon of the same class as the more widely known American-made Stinger.”