DJI has a FPV system called the AVL58, that includes a Video Transmitter and Video Reciever, you are looking at the Video Transmitter, working on 5.8Ghz frequency with 500mw output, able to transmit video for 1km~1.6km (factory claims), will take 3S~6S power input (11.1V ~ 22.2V Li-Po battery).
Connection is fairly easy, the Video Input is a Phone Jack plug, connect that to the DJI H3-3D Gimbal's GCU, and connect the T-Join to a 3S-6S power supply, you can remove this connector and solder the system directly to the drone's main battery.
DJI AVL58 Transmitter Specifications: