C-x 8 RET GREEK SMALL LETTER NU RET
C-x 8 RET lets you enter any Unicode char by name.
The char name you're looking for is GREEK SMALL LETTER NU.
If you use Icicles then you can find this character easily without knowing the exact name, e.g. the order of the components:
Type greek, then S-SPC to add another pattern.
Type nu, to see all matches for both ...