I remember seeing waves 1-4 at Target of the blind capsules. Series 1 and 2 of the five-packs at Target and Five Below. I was able to pick up the Macaron set from Target last summer as well, and I think I saw the 15-pack countdown set in store at Target as well? Those are it. I've not been to any Kohls or Marshalls to see if I can find other waves' five packs.
I think I saw some people with Series 5 stuff on Instagram, but they live overseas.