Bill, to back up Steve’s recommendations, I’d suggest a trip to a local Ace Hardware for a squeeze tube of Lexel, usually found hanging from a peg above the caulking supplies. A caulk gun version is also available if you expect to use a lot; I use it whenever drilling holes in my house siding, etc., also. Lowe’s usually carries at least the gun-size version, but not always the convenient squeeze tube.
The squeeze tube is handy for sealing anything... I use it for water-proofing in-motion Xmas light control modules for example; the only glitch is after first use, if not effectively capped and much time passes, the product tends to get viscous in the nozzle and the first inch or so thereafter is difficult to work with. Otherwise it is a superior sealant that’s even non-conductive, and I’ve used it to encapsulate certain corrosion-susceptible outdoor, low-voltage electrical connections.
Our Beaver’s windshield brow trough developed severe cracking years ago, and water appeared to an inch depth in the 12v electric bay, street side forwardmost. Filling the cracks with Lexel, with touch ups biannually, fully stopped that problem... you certainly don’t want water in that particular bay.
A moistened finger can also help cleanly spread Lexel beads around your new clearance lamp covers also. Replacing the cracked ones should’ve been a best first step in addressing your leaks. Of course, make sure all surfaces are clean for maximum adhesion. I also now regularly use Aerospace 303 on the clearance lights to help prevent UV deterioration.
Joel