To go along with my AR magazine rack (https://www.thingiverse.com/thing:3153602), I designed a similar set of Glock magazine racks. Keep in mind, these were designed specifically for 9mm full-size Glocks (17 and 34), but they also fit G19 magazines at a slightly different angle. These can be seen next to the 33rd Korean magazine in the second photograph. I believe .40S&W magazines will also fit just fine, but don't take my word for it.
There are two versions of the rack included. One is for completely stock basepads and the other is for extra-wide basepads such as the pictured Ghost MOABs. The wide basepad version holds eight magazines while the stock version holds ten.
As with my AR rack, this was made to be mounted with a set of M4 nuts and panhead screws, which can be found on Amazon below. Mount it however you like, though. Enjoy!
M4 Panhead Screw and Nut Set
Glarks 280-Pieces M4 Pan Head Phillips Stainless Steel Screws Bolts Nuts Lock and Flat Gasket Washers Assortment Kit
Printed with supports as oriented in .stl; 240C/110C