If you can't find Cosmoline brand or want an easier way to apply it, any of the frame-saver sprays are very similar compounds. I used LPS-3 on a motorcycle chain for a couple years and it seemed to work fine. It goes on slightly wet, carrying it into cracks and crevices, then evaporates to a sticky, waxy lube that seems to last well. The difficulty I found was that the spray valve on the can gummed up long before the can was empty.
Over on CGOAB
someone recommends "Squirt
." It was suggested to them by a Dutch bike shop, so they should know something about wet weather chain maintenance. I haven't tried it but I am tempted. The website advertises:
Squirt is a NEW GENERATION emulsion chain lubricant. It lubricates better, stays on the chain longer and keeps the chain clean. It is a wax based, long lasting dry lube that does not contain harmful solvents and is environmentally friendly. This liquid lubricant has unique properties, making it ideal for any cycling condition. It was developed to give better lubrication, last longer and keep the chain clean over long distances, for both mountain biking and road cycling. No degreasing is required or recommended.
PS - I'm presently using ATB (All The Best) that a mechanic at Bike Gallery recommended. It's red color, in a plastic bottle with an extendable drip tube. It comes out fairly thin, maybe about 5-10W, but it gets quite sticky especially after it sits for 15 minutes or so. Doesn't seem to fling off much.