Correct, stick with any 802.3at-compliant injector, preferably with a Meraki or Cisco SKU, but the key thing is that it's 3af or 3at compliant (depending on the model of AP, af power could be sufficient). The 802.3at injector Meraki SKUs are MA-INJ-4-XX and MA-INJ-5-XX where XX = US, EU, UK or AU and the "4" is the "regular" gigabit injector and the "5" is the multi-gigabit injector.