Just to say What I find useful : Ortlieb Panniers (but other companies make water proof Panniers )

I modified one set my bags to add webbing connecting strips so they come off as a pair rather than 2 separate bags

They come off the bike into the shopping cart, grocery checker fills them and I Put them back on the bike ..

I recently got another Ortlieb bag , their compact https://www.ortlieb.com/de/Ultimate6%20Compact/ for my wallet & eyedrops .

but they also have even more purse like bags too .. https://www.ortlieb.com/de/Velo-Pocket%20Urban%20Line/
https://www.ortlieb.com/de/Barista%20Urban%20Line/





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