To do this properly, you need a "matched" transistor pair in a single package. These components are widely available, though I don't have a part number avilable.
Best you could do without a single package pair is to match to separate devices and bond them face to face with super glue..both will then experience the same rise in temperature( well almost...)
It's working as a current source, it's just that the currents in the two halves aren't matched. The currents don't need to be matched to operate as a current mirror. It still has the high output impedance (that of the Q2's drain) and near constant current of a current source.