I had a similar set up on a GT, but with an oversized headtube.
Check the link above. Find the section: "Low Profile", "Zero Stack", "Integrated with Cups", "Internal Headset", "Semi-Integrated" types
Looks like one of those to me. You should be able to find one with cartridge bearings – but this means replacing the cups that are pressed into the frame (but it sounds like you'll need to do that anyway).
Note that you should measure the inside of the headtube to check if its an 'oversized' one. If so you may need an FSA Orbit Z or similar.
Another alternative is to do a google for "Focus bike-type headset" and see if anyone else has the same question / answer.