I bought one of these adapters: Ubiquiti INS-3AF-I-G
It is a converter that allows you to plug a passive POE device into an 802.3af (powered) POE switch.
It is especially useful if you have such a switch and want to reduce the number of passive POE adapters and AC power cords (e.g. Ubiquiti 25 volt adapters).
In my case, I used it with a Dell PowerConnect 6224P, 24port 802.3af switch for a Ubiquiti UAP-AC-LITE access point that is a passive POE device. It helped clean up the area with the reduction of the usual 24V POE supply + AC cord that we are used to.
The device is small, about 4-inches long and has an RJ-45 on each end.
I haven't yet used it on any mesh node devices but it should work on them as well.
(I didn't time it but it probably took me 10-15 minutes to upload the pictures as the process is not intuitive. And yes, I've done it before but quite some time ago.)
73 - Mike ab4yy