Would be grateful if anyone has recommendations for fully waterproof rucksacks, 30-40 litres. The Crux RK30 and RK40 both look excellent, if a little pricey, and will fit the bill if I can't find an alternative. I'm sure Exped used to do something similarly robust and no-frills, but the examples I've seen lately have used much lighter weight fabric. Doesn't necessarily need a roll top, so long as the fabric is that heavy duty shiny stuff like Ortlieb use for their panniers.
Cheers!