Here’s a basic selector,
https://www.russound.com/products/connectivity-and-control/speaker-selectors/dual-speaker-dual-sourc...
You could also look for a Niles SAS-1 or a Niles SPK-1. These are no longer available new but can be found used. They would offer options for switching automatically.
As I posted this, I just noticed Al's post. Hopefully he will see my post and comment if my suggestions are suitable.
https://www.russound.com/products/connectivity-and-control/speaker-selectors/dual-speaker-dual-sourc...
You could also look for a Niles SAS-1 or a Niles SPK-1. These are no longer available new but can be found used. They would offer options for switching automatically.
As I posted this, I just noticed Al's post. Hopefully he will see my post and comment if my suggestions are suitable.