You can also fill out the missing emblem form and wait for them to be unlocked.  My last one took a week and a half to unlock.  Contact Activision Support for the link to the form.  Be sure to save the link in your favorites because you will have to fill out this form every time you need an emblem unlocked.

SUM1SLY83's suggestion also works but it can be impractical if you have a large clan.