This project creates encrypted backups for Bitwarden vaults including attachments. It pulls your vault items from Bitwarden CLI and download all the attachments associated with those items to a temporary backup folder. Then, portwarden zip that folder, encrypt it with a passphrase, and delete the temporary folder.

It addresses this issue in the community forum https://community.bitwarden.com/t/encrypted-export/235, but hopefully Bitwarden will come up with official solutions soon.