I've used
these and
these and haven't had a problem with either.
The first has the advantage of only using one port off the NVR/switch. Most cameras, non-PTZs, don't draw more than 8w so you'll be fine. You can also cascade these devices. They do get a bit warm but I live in the Caribbean and haven't had an issue putting this in a waterproof box in the heat. It draws 3w according to my Dahua NVR. Zero failure after 6 months.
The second ties up two ports off the NVR/switch but the actual device is inside. It doesn't get warm at all and you can use the full wattage of each port.
It would also be possible to use both! First the second device and then one, or even two, of the first off the y-connector.
More than that, an outdoor POE switch. But these devices have saved me running cables and both are cheap.