Indicator fuse blowing in hot weather

[Intruder]

Hi again, I believe I've come to the conclusion that the seals around the rear lamp casing may have perished, I've yet to check the seals myself but I'm having water leaking into the boot and this is as I've found out a very common fault. I'm just wondering if anyone can point me in a direction of where to find replacement seals for both the light casings and for the tailgate (just for extra measure).