Greg Cote has always been my first stop when looking for magazines. Pricing is fair, shipping is fast.
https://www.gregcotellc.com/cart/index.php
http://gregcotellc.com/cart/glock-factory-magazines-c-94/glock-43-factory-6-rd-9mm-magazine-g43-glock-mf43106-p-1598.html