WD-40 is NOT A LUBRICANT. *grumbles* Water replacement? Yes. Pretty good solvent? Yes. Lubricant? No.
And, yes, the answer is a small bottle of chain lube. I've got two bottles from... oh, probably a decade or so ago. They're still going strong.
Oil the chain, ride for a while to disperse it into everywhere, wipe the rest off (or don't, if you're lazy).