Don't remember the brand but got a single mag holder (hard side) with a spring-clip for about $12 from Bo ..... (they whose name shall not be mentioned).com. It was a friction type that held the mag very well.
I tried to make one myself, out of a knife pouch of all things..
Worked great for about 2 whole hours.
I am now in the process of trying to find a single mag pouch for a reasonable price, since I only have two 15 round mags and one of them is in the 19 when I'm carrying (even though I could legally carry the 33 round mags, I'd prefer not to when CCW'ing.. lol)
I use a old cell phone holder, holds two 13 round G23 mags or one mag and a 5.11 ATAC-A1 flashlight, which is how I normally carry it...I figure 26 rounds and a flashlight is better than 39 rounds and in the dark....plus it conceals very well...looks like what it is supposed to look like....a phone holder..
Nylon velcro flap made by Pass Port. Weak side OWB with the clip. When I carry my G19 I use one that will hold a G17 mag w/a plus 2 and when it is my PM9 I carry one that holds the 7 round extended. Sort of discrete/stealth if I have my shirt tucked in.