Get registered on GlockTalk and throw up a WTB. It has a huge active membership. I got 4 G17 mags for $16.00 ea and free shipping last year. Probably an unreal price now but better than retail if even available.
We (Acme Sports/Seymour) have a bunch of different Glock mags currently in stock for $30/each. The only ones we are currently out of are Glock 19 mags.