you can by a putty type sealer form car accessory stores to that will do, remove the lights completely and get rid of the ld seal and replace it with the putty, but it would be wiser to try and locate the leak before spending money on possible cures, I have spent many long shifts tracing water leaks in many different cars, easiest way to look for a leak is to go to the area you suspect it is coming form and start form there, fold down the rear seats and remove the boot carpet , lie inside the car with a torch and get someone to use a hose all ocver the area, including coming up form underneath, as sometimes its road spray that gets in, once you find a leak , then you fix it, dry off the affected area and check regualrly incase there is more than one leak which there usually is.