Not familiar with devices that switch just optical audio, but haven't been looking for one either. There are several devices that will switch both component/composite video AND analog/digital audio. If you think you might have the need for switching component inputs down the road, it may be worth going with a switch that will do both now rather than buy a separate device later.
You don't mention how you want to activate the switch, whether manually or by remote or automatically, this is going to make a big difference in the cost. A quick google search produced manual switches for around $30.
I bought the Audio Authority 1154 to switch component video (it also switches audio), for about $180 and it works like a champ. If you think you might have a need for component switching later, you might want to take a look at it or comparable products.