The only ones I know of are out of production:
http://www.emmlabs.com/html/products/switchman/switchman.html
http://www.emmlabs.com/html/audio/switchman3/switchman3.html
Perhaps you can find one.
http://www.emmlabs.com/html/products/switchman/switchman.html
http://www.emmlabs.com/html/audio/switchman3/switchman3.html
Perhaps you can find one.