Replacing a transistor in a CCFL inverter circuit
You'll have a tough time finding an NPN transistor that meets all the specifications of that one in the same package, but you may not need that. The particular transistor you linked to has a relatively high beta (min 240 at 500mA) and a relatively high breakdown voltage (80V) without resorting to a darlington structure.

A BC639 can do 100V but it doesn't have the same beta (typ ~80 at 500mA) so the transistors will burn a little more current. This shouldn't be a problem, however, if the output power is not much. I'de try that one (it should be very easy to find) first. If you find it's getting too hot, try a FET or a darlington NPN.

Alternatively, the 80V rating may be overkill. If you can test an operating version of the circuit / find a schematic / reverse engineer it, then you could find something in 60V operating range which is more common...