It's difficult to find out exactly without going through forum posts, which is why it would help all if it was validated.
Here are some:
Netgear WAC720/WAC730/WAC510
Netgear EX7500 and EX8000 support at least 802.11 k.
Linksys EA7500, EA9500, RE7000
In my mind the WiFi back-haul solution...