If you want DSA, you have two choices:
1. Buy directly from PMK.
2. Wait for a group buy.
There may come a time when somebody puts up MaxKeys DSA or XDA keycap sets up for sale on an on-going basis the way PMK does, but I don't know of any that do that now. In terms of cost, the cheapest option would probably be a group buy for MaxKeys DSA, followed by a group buy for XDA.