2 motors 1 esc
I suggest you try maplins http://www.maplin.co.uk/. Look under components/capacitors and you want the second page ceramic capacitors 0.1uf.
If you have a local outlet it will be quicker.
You do not need a dual ESC two identical ESC's is the way to go.
If you are considering Mtronik look at http://www.mtroniks.net/cat/ex-demo
I have used several of their ESC's and they work well. The ex-demo refers to ESC's that have been tested to spec, so you do know that they will work.
Dave
Dave