I think that all R&M deal can have the Birdy Carry Bag. Kemper Fietsen in the Netherland has it too.

I bought it and send it back because my main goal was to have a bag to carry the Birdy folded and this bag is very thin not very good to carry the Birdy folded inside.

There was a previous version of Birdy carry bag from R&M much stronger not available anymore but often for sale on .ebay-kleinanzeigen.de. Of course, due to the thicker material, this bag is bigger and heavier when folded.