Your parts bin most likely has the makings for one of these: Joule thief - Wikipedia
They are not magnificently efficient, but you might get 100mA from one. You'd have to add a diode, smoothing cap, choke, and linear regulator to the mix.
1.5V on the input is quite a low voltage. Potential parts-bin items like a 555 charge pump or leveraging the charge pump on a MAX323 are out.