if cheap is the main thing you can get one from decathlon. They do fully waterproof fully unbreathable type things for almost nothing and probably quite decent things for not much more.
Otherwise I saw finisterre had some discount smocks recently if you're an S or M
Unless they've made changes, the hoods on those finisterre waterproofs are terrible. No way to cinch down onto your head, so don't stay on in the wind, and don't move with you when you turn to look over a shoulder.
if cheap is the main thing you can get one from decathlon. They do fully waterproof fully unbreathable type things for almost nothing and probably quite decent things for not much more.
Otherwise I saw finisterre had some discount smocks recently if you're an S or M
https://finisterre.com/products/mens-lucas-beaufort-x-finisterre-rainbird-smock-navy-mosaic