Midway sent me an email. Gen 4 Glock 17 and 19 mags for $15.99. Their shipping is a little high but it's super fast.
http://www.midwayusa.com/s?promotionid=1113675&cm_mmc=pe_brand-_-glock-_-17_19magazines-_-20170222
http://www.midwayusa.com/s?promotionid=1113675&cm_mmc=pe_brand-_-glock-_-17_19magazines-_-20170222