It is limited edition, so in general you have to find someone that has one. It can be traded. There's usually an event around Oktoberfest that also has them available in packs again. Functionally the Dwarven Beermaiden is the same rune.
I can trade you one for something of equal value or better. https://www.poxnora.com/trader/viewtrade.do?id=3874878
Anyone got Poxtoberfest Maiden or Maeck the Unshakeable for trade? https://www.poxnora.com/trader/viewtrade.do?id=3875157&fb=0
