Have you checked to see if your switch supports 802.11 AT POE?
AKAIK nothing exists to combine two 802.3af to a single 802.3at port. If anything does exist it is a jury rig and definitely non-standard. An injector is likely your best option if you want to keep the switch in place.
I would use a PoE+ 802.3at injector. Make sure to disable PoE on the ports, otherwise the injector won't actually send any power.
If you power the injector up, and then plug it in to the switch, the PoE+ camera will be powered. However, if there is a power failure/reboot, when the switch powers up again, the injector may detect the power from the switch and NOT send PoE+, but pass the PoE from the switch, thus the camera will not power up.
The alternative, is if the switch has any non-PoE ports, to use them.
Make sure to label the switch or port, so down the road you don't think it is broken if there is no PoE coming out of those ports...