If you are talking about the hi-cap ones - IE. 10/33+. I think this question might be better served in the black rifle forum, since these are typically purchased by guys that own JRC, TD or any pistol cal carbine that takes glock mags.
I know a lot of people that own glocks (myself incl) only have glock mags, whether it's 10/10 or 10/17+, and they work flawless and readily available at local & online shops.