Here is one that you can hook up two amps and two sets of speakers also if you want.
http://www.ebay.com/itm/TC-7220-2-Way-Amp-Amplifier-Speaker-Selector-Switch-Switcher-Comparator-Router-/391073502625?hash=item5b0dcc15a1:g:ccgAAOSwPhdU9yws
Or you can go the cheap way and use this one back to front.
http://www.ebay.com/itm/A-B-A-B-Switch-1-IN-2-OUT-2-Way-Stereo-Receiver-Speaker-Set-Selector-/152373329362?hash=item237a287dd2:g:Q9gAAOSwNSxVbL5-
Cheers George
http://www.ebay.com/itm/TC-7220-2-Way-Amp-Amplifier-Speaker-Selector-Switch-Switcher-Comparator-Router-/391073502625?hash=item5b0dcc15a1:g:ccgAAOSwPhdU9yws
Or you can go the cheap way and use this one back to front.
http://www.ebay.com/itm/A-B-A-B-Switch-1-IN-2-OUT-2-Way-Stereo-Receiver-Speaker-Set-Selector-/152373329362?hash=item237a287dd2:g:Q9gAAOSwNSxVbL5-
Cheers George