I will recommend you a perfect product for your application. POE-Extender02, it can feed two poe cameras with one network cable.
Up to 200m PoE transmission, or max 300m with cascade deployment 2 Port PoE extender, running one ethernet cable to connect to 2 IP devices IEEE 802.3af/at PoE IP Camera Support Compatible with 60W High PoE Midspan Small size (79x52x23mm), lightweight, fits into regular camera back box. No power...
eu.linovision.com
I have used it, it works very well. You can have a try.
I recently installed one of these and it's working flawlessly. The manufacturer (or some of the manufacturers) says max 8W per port but I'm using just a bit more than than 8W in one port and 4W on another without issue.
I've also installed one of these:
EVERSECU POE Combiner Splitter Adapter, Run 2 IP Cameras on 1 Cable, self-Adaptive Compatible with 12/36; 45/78 Powered POE switches and POE NVRs
I prefer this as the device itself stays inside beside the NVR/switch. Only the splitter is outside.
Downside is that a cable with a female jack/keystone may be required if the cameras are any sort of distance apart.
It's also half the price of the splitter.
This allows me to use the 25.5W max output that my NVR provided. So I can even power an
IR illuminator off the same port.
So far, so good with these devices. Much easier than running another cable.