B&H Photo has all the Zeiss lenses for Canon and Nikon.
The Zeiss 21mm f/2.8 Distagon is an wide angle lens offering a strong visual impact. It is competitive with the best Leica M ultra-wides but has a digital friendly ray angle, so there is no performance loss on mirrorless cameras, or on Leica M 240.
This series is shot from the same vantage point as the 18/3.5 Distagon series and the 15/2.8 Distagon series, thus the three form a useful triad (15/18/21) to compare. See also the 28/2 Distagon series.
In Guide to Zeiss:
Includes the usual HD and UltraHD images and generously-sized actual pixels crops.