Ok, so this is kinda stupid. I just got my achievement for my 1000 garrison missions .While doing those missions I've done like 150~ Rare missions . I only got 1 Certificate . I had some ideas of how we should be able to get that item. 1)Blizzard should make the item drop from work orders with 2.4% drop rate. 2)Let us buy a small amount of those per week via Garrison Resources. 1st Follower Re-trait Cert. = 100 Garrison Resources. 2nd Follower = 200 Garrison Resources. 3rd = 400 Garrison Resources. They shouldn't add both of those ideas , but 1 of them would be necessary. If you have more ideas, share them with us .