I fitted one of those to my 500 and it had a rubber grommet on the original, which I could not use on the led bulb due to it's huge bulbous end(the fan part), so I used some foam rubber sheeting, wound it into a tight circle to be the same the diametre as the original grommet.
That covered the end of the globe.
I then stuffed the excess cabling and original fitting in there too, and sealed it up with some refrigerant pipe sealer tape (really sticky and stretchy)
Obviously a real mcguyver story, but since it is out of sight, it is out of my mind, as more immediate important things take precedence.....
It has been on for 6 months now , with zero issues.
Sent from my Samsung Note 3 with Tapatalk