One option is to have open sights that co-witness with your optic, but these can be distracting and work best with zero-magnification scopes. XS Sight Systems has developed an ingenious solution that will work on any AR with a full-length rail called Angle Mount Sights.
XS' Monty Long, a serious competitive shooter, worked with Andrew Brady of Lone Star Armory to develop this sight system, and after trying them on the Mossberg MMR, I believe they are indeed a grand solution. Essentially, these sights clamp to your upper rail and extend slightly out to the right. On a pedestal from the base, there is a platform with a 45-degree angle. The front and rear sights are mounted on their respective pedestals. The rear sight emulates the rear sight used with XS Big Dot pistol sights—a shallow V with a white line at the center, which is adjustable for windage. The front sight is a post with a rounded top and a .14-inch white circle surrounding a tritium vial. It is adjustable for elevation.
These sights are fast to acquire and you can mount them to provide whatever sight radius best suits your eyes and coincides with the scope mounts for your optic. To use them, all you need to do is rotate the rifle to the left 45 degrees and they are right there in front of your eyes. You can even zero these sights to compensate for the drastic off-set encountered with AR sights at close range. MSRP is $150.
