I'm not Jim, but I know he uses the Dometic Milenco Aero3 towing mirrors.
I towed it home without tow mirrors and found the visibility to be acceptable for regular highway driving, especially if one adjusts mirror position appropriately. The Sport 22 is the only narrow-body Airstream in their lineup, measuring at 87.25" wide. The Model X mirrors extend 89.4" (albeit that number includes the housing), so coverage is decent.
I am planning to install a rear view camera to supplement my factory mirrors. I will continue to consider the Dometic mirrors that
@JimVandegriff uses, as they do appear to be the best choice for the Model X, but I would like to limit my aerodynamic drag. So long as my safety doesn't feel compromised, I will continue with the stock mirror/rear camera setup.