I got a lightweight leopard print one from Lands End last year.
Very waterproof (withstood wet Welsh holiday) but doesn't have any air vents, so only recommend if you're not going to be too vigorous.
I can't see one like mine on the website; they have a few styles which are billed as water resistant. They have one waxed cotton parka style that is billed as water repellent, and one fleece-lined one described as waterproof.
If you want light-weight and v waterproof plus ventilated, and can spend £££, try the outdoor brands Arcteryx and Innov8 (stormshell)