Replacement Headset for FSA Orbit i-T

I've recently purchased a 2010 Cube Agree GTC frame and fork combo, planning to build it up with a smattering of older, unused components.

I've run into a snag trying to find a replacement headset. The original component was an "FSA Orbit i-t", which is no longer purchasable. I originally tried the following,

http://www.wiggle.co.uk/fsa-orbit-15-zs-1-18-black-aheadset/

but the LBS said that it didn't fit, and merely directed me to several bike shops that had the original part listed, but out of stock.

Any help in figuring out how to proceed would be most appreciated!