I ordered CIPA mirrors from RealTruck.com (if I recall correctly).
Went through their site menu for my specific truck. Came in a couple of days and were a perfect fit for my application. Very impressed with the quality.
I don't think most retail outlets will carry enough stock to fit all brands/models.
2015 Shamrock 231KSS, Oyster shell
2016 Chev Silverado LT Z71 Ext. Cab, 4x4, 5.3L V/8
Reese Straight Line WDH, 2000W Honda Gen.
2 Old Town kayaks & 2 Boston Terriers - Zoey/Gonzo
Lar & Ruth
55 nights camping in 2015, 45 in 2016