Do they sell duck breast here?

Have never seen duck at WinCo. Try Wal Mart, Whole Foods or Costco. (You do not need a Costco membership. You can shop at Costco online, but they add a 5% surcharge for non members. Or ask to go with a friend who has a membership.)

I suggest calling the store and speaking to someone in the meat department. I believe I've seen duck there, but product selection may vary by store.