We have the Sidebar Widgets package installed, "Ultimate Picker", and have this working just fine.

However, I'm a little stuck. We will be slowly upgrading the websites and adding new Sidebar widgets but during testing, when we have created new sidebars, the older websites don't show the new sidebar creations and thus not selectable. 

In order for a website to show the new sidebar option, we have to create a brand new site and copy over all content over in order for the new sidebar option to show.

Is there another package or something I am missing that will automatically add new sidebars to a document type whenever they are created?

I hope this makes sense.

Cavan