I would try using led blinking + binoculars. Or camera with good zoom
You could also use some signal analytics tool. Assuming your connected to the closest AP/ strongest signal you could see the mac of the AP in the tool. To make sure you could reboot the ap and see if you lose signal to the bssid mac
(Side note: Mr44 are not really ment to install very high, but maybe it works out fine in your case)