AFAIK they're not that tricky to fit, but you may need to cut off a bit off plastic on the light to make them fit better
Erm posted this in discussion:
remove one of your red lights and have some card ready......
trace the edge of the water guard onto the card.....cut it out and then thats your template for the light.....
draw it on.....cut it off.....use a bit more force

and bada boom bada bing......