Is there a way to get the the zipball's size of a branch?

I’m trying to make my own installing system, that will download the source code from the “production” branch of my repository.
But before my installer program will download the zip, I’d like to add a confirmation box that demand “we wil fetch xx Mb. Confirm ?”.

The problem is : after searching, I know how to get the download link from the API, but I still don’t know how to get the total size…

Requesting{user}/{repo}/zipball/production will just redirect to a download link.
Having something like

 "download_url": "",
 "type": "zipball",
 "size": "68Mb"

would be perfect for me.

Thanks in advance !!