Most folk on here would plump for Ortlieb back Rollers at a guess. Around £130 a set. Bombproof. I have a set which are about twenty years old and have brought the weekly shop home most weeks. Just starting to need a few running repairs.
ive a set of Arkel Orcas for touring. These - the 45s - might just tip your budget, but they are supremely well made and completely waterproof. Arkel’s randonneur rack and bag is a brilliant bit of kit too, but more of an investment for long trips.
You will be unlikely to find Arkel on Amazon, I fear; but they will be delivered in a van. I bought mine by sailing to the Canadian factory on a raft I made in the shed from micro plastics and old knickers.