I want to suggest to whoever wants to try to go to grocery store by bike, to check these bags.

Right now there is s promotion (which hapoens regularly BTW) so you can get 2 for 14€

On the plus side:

• foldable and light
• cheap
• made of recycled plastic

On the cons side:

• not waterproof
• can be a little cumbersome riding (but much better than having bags hanging from the handlebars)

.