(https://i.imgur.com/9KfVNrQ.png)
Pogo has re-released 28 previously-retired Mix-n-Match badges and are on sale for 8 - 10 gems each.
This sale is valid through November 7th.
https://www.pogo.com/challenges?filters=MNM%2CON_SALE%2CUNOWNED&sort=RELEASE_DATE_REVERSED