I'm trying to find a cost effective solution to mounting a red dot on my SGL-21. I've concluded that an Aimpoint T-1, althought the best option, is out of my price range. I am looking for a quality sight in the $100-$250 range. I have an Ultimak gas tube replacement rail to mount the sight on. Co-witness ability would be best, even if it's lower third. As always, your suggestions are greatly appreciated.