The Ultra 4800 has such functionality. In fact it has two such buttons. And is it available as a replacement remote in the Roku store. It's called the Voice Remote Pro, and will work on any Roku player that supports WiFi Direct remotes. To see if your player supports such a remote, go into the Settings menu and see if there's a Remote menu. If your player doesn't support such a remote, I don't think you'll find a remote menu.
Dan
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee, just another user.