Michelin City Grip all the way. P or S rated. P is rated at 94mph/150kmh, and S is rated 112mph/180kmh
Revzilla has decent prices, as does Bike Bandit. I'm sure there are other sellers out there, but those are my two go to places.
For the record, and for easy access, here are the pertinent specs for the tires:
X400i Tire Information
Front: 120/70-15
Cold Tire Pressure: Front: 2.00 kg/cm2 (28.4 psi)
Rear: 150/70-14
Cold Tire Pressure: Rear: 2.25 kg/cm2(32 psi)