Pogo has re-released 45 previously-retired Mix-n-Match badges and are on sale for12 gems each until March 6th, 2020
To find these badges easier, sort by "Retires" and look for the badges marked "Re-released".
These badges were originally released in January 2008 and September 2018.
https://www.pogo.com/challenge/find-badge.do?searchtype=mnm&sortName=expires&sortDirection=true
(https://i.imgur.com/o9m6O6V.jpg)
You're welcome!