According to the ATF database, there are 4 registered FFLs in Sunnyside, Washington.
615 YAKIMA VALLEY HIGHWAYSUNNYSIDE, WA, 98944
110 W SOUTH HILL RDSUNNYSIDE, WA, 989440000
1719 MORGAN RDSUNNYSIDE, WA, 98944
450A STATE ROUTE 241SUNNYSIDE, WA, 98944