I didn't make it, but I bought a 3-D printed mag loader, made by Tacshots.
.
This Universal Mag loader (large), $8 on fleabay, was suppose to fit the mags for my Ruger American(45acp). When I got it, I found my mags didn't quite fit, but it was real close. After looking at it, I figured if I could modify it without wrecking it, I would be good to go.
.
I wasn't sure if this plastic was a thermo-plastic or more of a epoxy type of plastic. It wouldn't work for me as is, so I got the torch out, and heated the short side and forced the mag inside and let it cool. Works great, it's a snug fit, but that almost makes it easier to use.