I purchased "saddle bags" from these folks. They have two versions - "Stallion" and "Colts". You can cram the former with 45-litre junkie while the latter with 37-litres.
Their saddle bags can resist incessant rains lasting to 4 - 5 hours. The store keeper told me that the bags are designed to withstand "normal" rains. I asked him what is his definition for "normal" rain. His reply - a smile.
I guess that should make Henry Fonda and Dennis Hopper happy on sub-continental roads.