What you could do if you really want to use G19 mags in your G17 is to saw off the magazine well about 1 inch (or whatever the size different between the two model is), I have seen people doing that mainly for conceal carry.
This way you get the longer barrel of the G17 but with the shorter grip of the G19.And you can either use G19 or G17 mags in it.
Just a thought.
If you got 2 or 3 of those, enough to make it worth your time, it might not be hard to find someone willing to swap with you. What you have would fit the G19 and also work in the G26, (2) popular models...