Rain covers for all Bihn backpacks sound like a great idea.
Original designs. Made in the U.S.A.
Alosaks...Navy Seal approved...will tote most things and are water proof. Available in various sizes at Amazon. If we are talking standing in a downpour....Alosaks and/or a travel umbrella (the latter of which will not be utile while riding a bike).
Synapse 25 Steel D/Wasabi, Side Effects: Black/Wasabi, Steel D/Wasabi; PCSBs in UV, wasabi, and steel; Large Shop Bags: 2 Nordic, 2 Solar; 2 sm. Shop Bag UV; CoPilot Black D/Wasabi; black D/wasabi Pilot; 3 Travel Trays; 3 Clear 1/4 packing cubes;
wallets; number padded pouches and clear organizer pouches, key straps, double carabiners galore, and soon to be the mother of an aubergine/UV SE AND an Aeronaut Junior!!!!!!!!! (Darcy says soon.)