SPDIF Motherboard Port

[smush]

Hi
I'm wanting to hook up my PC and MacBook Pro 2009 to one monitor and one set of speakers. On the monitor side I have two HDMI ports at the back so I'm going to plug in a second cable and connect it to the MacBook the monitor's OSD Menu let's me select between HDMI ports 1 and 2. The audio is where I get a little confused. At the moment my old Altec speakers are hooked up to my PC with a 3.5mm jack, I've read that splitters are a bad idea but that a switch box should be ok however I cannot find one?

After looking at the back of my Altec box which the speakers are hooked up to (is it called a subwoofer? I don't see any speakers on the big box) it has an SPDIF port so I was thinking of hooking up the MacBook to the speakers using 3.5mm jack and the PC using SPDIF since I have an SPDIF Out port on my motherboard but when I search Amazon for SPDIF cables they don't look like they would fit the port on my motherboard I have attached a picture of the speaker's ports and and the motherboard's I know I'm going wrong but I can't figure it out. Thanks

http://imgur.com/DlS1c4A

http://imgur.com/UP4Qo39

 

[Mister_MO]

This is called toslink, so look it up. Btw, 3.5mm switch is easy to find, here is one on ebay for inspiration so you know how is it called.
http://www.ebay.com/itm/2-PORT-3-5mm-STEREO-Manual-Sharing-Switch-BOX-Audio-Speaker-selector-way-2-1/111110123606

 

[smush]

This is called toslink, so look it up. Btw, 3.5mm switch is easy to find, here is one on ebay for inspiration so you know how is it called.
http://www.ebay.com/itm/2-PORT-3-5mm-STEREO-Manual-Sharing-Switch-BOX-Audio-Speaker-selector-way-2-1/111110123606

I don't think it is TOSLINK because I googled it and the cable end has a round pin sticking out of it similar to 3.5mm but as you can see from the back of my PC it is more square it also says SPDIF above the port.

The product in that ebay link would be ideal but I don't reside in the US. I found a similar one on ebay in my country but would have to pay import tax from South Korea which I don't really want to do.

 

[Mister_MO]

Some call it spdif optical, some call it mini toslink. I thought you would find it in google pictures as they most of time get random mishmash where is everything, but never mind. That switch i posted just you know how it is called on ebay and that it exists.