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, Imago Plum/Hemp/Steel, Side Effects: Black/Wasabi, Black D/Wasabi, PCSB in UV, Large Shop Bags: 2 Nordic, 1 Solar; 1 sm. Shop Bag UV; CoPilot Black D/Wasabi; 3 Travel Trays; 3 Clear 1/4 packing cubes;
wallet; number padded pouches and clear organizer pouches, key straps, double carabiners galore, a Black D/Wasabi Pilot, and soon to be the mother of a Aeronaut Junior!!!!!!!!! (Darcy says soon.)