Pogo has re-released 50 previously-retired Mix-n-Match badges and are on sale for 12 gems each until June 18th, 2022.
To find these badges easier, sort by "On Sale" and look for the badges marked "Re-released".
https://www.pogo.com/challenges?filters=MNM%2CON_SALE%2CUNOWNED&sort=RELEASE_DATE_REVERSED
I got a couple for 400 pogis. I might consider a couple of the 300 pogis badges. I have two weeks...
I'm going to pick up a few as well. Oh and yes, no rush on those 300's ... we have lots of time still.