I wasn't able to find the antennas anywhere either so I search some variance of it and bought 2 to try because they were so cheap. (link is at the end).
They are thinner than the ones in the P3S and don't fit quite perfectly into the slots but I was able to use Hot Glue to stabilize the antennas. Also, the antenna wire is a lot longer but can be pushed into the fuselage.
They also have the right connection to the gimbal but difficult to snap in by hand. I used medical tweezers to hold the wire in place and another pointing device like a screw driver to press the connection down till it snapped on.
After making the connections and powering on the P3S, I was able to see the drone broadcasting from the DJI Go app. Problem, I reset the Broadcast Name and forgot the password I used to connect to it. So I had to go through and reset the WIFI link to factory default. It didn't work though. At least not until I fully charged the RC Controller as well as the P3S battery. I got lucky.
Note to self, if you ever need to reset the WIFI to factory default and it doesn't work as indicated in the instructions and all the videos, ensure you fully charge your RC remote and Phantom battery.
Once the WIFI was reset I was able to connect to the camera. Just needed to calibrate it after that.
I did a few small test flights up and down the driveway with no issues. I have not flown it further yet due to weather conditions. The signal though shows up as good in the app with my Samsung Galaxy S7 sitting right next to it so I am a little nervous what it will do on further flights.
Link to the antennas Not too shabby for $5.00.
(
2.4GHz Antenna - Adhesive (U.FL Connector) - WRL-11320 - SparkFun Electronics)
Below is the information
SKU: WRL-11320
Product Name: 2.4GHz Antenna - Adhesive (U.FL Connector)
If you Google search 2.4 GHz Antenna U.FL you will be able to find different shapes and types all with the type of connector needed to attach to the gimbal. I knew there had to be more resources out there because of all the robotic building going on and FPV Racing Drone hobbyists.
Now the question is this...
Will it work with a 5.8 GHz Antenna that will produce better video feed with less lag and better range? I may test this theory out but it was a pain in the *** taking the drone apart. When you do this, map out which screws go where. I didn't and it took me a lot longer to put it back together. One of the reason's I am hesitant test the 5.8 GHz. Plus, will it interfere with RC 5.8 GHz controls. That would suck.
This all resulted from a crash my drone took while flying into a backstop in a baseball field. I had my dog with me and wanted to keep him from running off. I was fortunate the gimbal and camera did not break.