I would go ahead and get the mags now while you can. Can never go wrong with the 17 mags. They work in 17, 19 and 26. Even fit in my buds Kel-tec "rifle".
Pic of the G17 toG19 spacer, not a bad idea, but not that great either, Watch the lower edge of your hand when inserting mag. For me it requires changing the hand to grip position to avoid getting pinched.
I use this mag for carry and a 15 round as a spare.