No it's fairly easy to find the mags..
I think KSC/KWA produses the Glock series in batches, it's not discontinues as far as I know.
I don't own the G17 but I have 3 KSC G18 and one of them is my most used of all pistols I own.
I use it since the very first I ever played!! And I carry it with me at all skirmishes!
Wolf