We carry two different size/styles of Ostrich Rain covers. Both styles fit the Gilles Berthoud GB25, the Ostrich Rando F104 & F106 AND the Ostrich S-2 Saddlebag
Made of the same nylon material you see in your tent rain fly.
The large has a buckle strap for adjusting and the medium/small works just like a shower cap.
Either cover can be attached without having to remove your bag from your bike.