Connect 3 iMac 21" Screens together? What's the best solution to connect 3 iMac screens together so they're all usable as one large screen.

I currently have 2 iMac's connected together via a single thunderbolt to thunderbolt cable (Which works fine, mouse goes between the 2 screens etc).

However my 3 iMacs only have 1 thunderbolt port each so there's no spare port to connect the 3rd screen.
Similar image to the ports available on the 3 iMacs:
What you will need is splitter so you can connect 2 displays to your Thunderbolt port so you can use the both iMac with Target Display Mode. 

It's the only way to use these iMacs as screens.