Struggle for Catan card sizes
According to this post on boardgamegeek.com:


  SwanPanasia 'Standard USA' 57x90mm sleeves are reported to fit these cards perfectly. They are, however, larger than similarly-sized sleeves from other makers, so those other makers 'Standard USA' sleeves may or may not fit these cards.


Those card sleeves can be found for sale on SwanPanasia's site. Standard or Premium.