Have set up my TL-WPA 7510 kit with one extender and all is well.. All lights green. I purchased an additional extender (AV600 Powerline WIFI extender) and attempted to pair it with the existing...

Have WPA7510 Kit installed but want to add another extender. Can I purchase another extender by itself? If so, what extender do I need and where can I purchase it? thank you