This is my own design. It is designed for an S&W M&P 40. I know it will fit the 9mm version of the S&W and will likely work with other double stack mags.

There are two parts and are designed based on printing with ABS and then fusing them together at the angle you prefer. I have not tried to print with any other material but could potentially use anything else and then glue the two section together.

The screw is an m3 and there is a slot to drop the m3 nut in.

Also I have attached two version of the files one includes a base heat shield. This helps with my open printer to print without warping.