Made by Raven Concealment Systems, this wedge is made from a moderately dense rubber and attaches with two posts/screws. The hardware is supplied with the wedge. It was designed to fit the RCS Eidolon, and I cannot guarantee that you can make it work with any other holster. You will need to select whether it’s for a left or right handed holster as it’s not ambidextrous.
If you want a closed cell foam wedge that is universal, you can find that here.