I use ping pong balls cut in half as FPV antenna protection.
For this purpose I have designed 3D-printed lowers that fit the kind of 3 and 4 winged antennas sold on EBay and many other places. The antennas are pretty generic and should fit a lot of other types too.
The lowers are secured to the ping pong halves by some dabs of thin super glue around the edge. The antennas do not have to be glued in place.
A quick tip: It is quite easy to give white balls some color by dissolving the ink from dried permanent marker pens in some rubbing alcohol and then dipping the ball halves in the spirits.