Sporteque carries imported Glock mags that are internally blocked, and at great prices ($40). They don't have anything in 9mm right now, but I would give them a call to see if they expect anymore (best Glock mags ever). They are Gen4 double stack with full length springs so loading the 9th & 10th rounds is much easier, and no rivet to stick, or cause wear on the internals of the mag (best Canadian Glock mags ever).
P.S - I have a G17, 2-G19s and a G26, all the extra mags I buy are for a G17. They are easier to handle and load into pistol, they work on all 9mm Glocks and also easier to resell later if you decide to change platforms.... just saying.
I do realize you may want G19 specific mags, but other than a few suppliers they are not easy to find new.