Summer waterproof jacket that folds-up tiny?

Expecting rain, I wore my Endura Venturi eVent jacket; whereupon the sun blazed and I did my boil-in-the-bag impersonation. (It wasn't that bad, really; the Venturi does 'breathe' well.) So I'm after a proper lightweight, small-folding waterproof, please.
Thanks, all.
Zip'.
Thanks, all.
Zip'.
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