If you have a Glock MOS or an RMR/optic capable slide, you should have a good set of co-witnessing sights. These Ameriglo Suppressor Height Night Sights are basically the best, and cheapest, version on the market that I'd recommend. Check them out.
In the photo: Thompson Leh Glock 19 Slide, USA Flag Pattern thread protector
, Streamlight TLR8