Anything i put in the side cases usually isn't something sensitive to weather. And if it is (a bag of clothes lets say) like CCR i wrap the rucksack...
IIRC they are a standard H7 fitment for Low & high beam, so anywhere sells those. I recommend the Osram Nightbreaker bulbs - Amazon generally have a...
Probably best to do that first and make sure it's not causing any excess air to enter the combustion chamber. Also check the ICV vacuum hoses are not...