I tried to find 2xAAA direct diode green laser pointer at Aliexpress, which are 520nm, and didn't found any: https://he.aliexpress.com/w/wholesale-520nm-laser-pointer.html?spm=a2g0o.productlist.search.0
Why?

Probably the laser diode needs higher voltage, Copilot found 5..6V forward voltage. That could be easily generated by "x2" charge pump (a single capacitor with a single IC can drive the laser diode) from 3x"1.5V" or 1x"3.6V" (about 2.7V minimum), but would need something more complex and so more components from the 2x"1.5V" (so about 1.8V minimum, so would need full boost, so at least two capacitors, inductor and IC).

@Medved: Why that a green laser diode would need higher voltage than IR (For pumping a green DPSS laser), red, blue and violet laser diodes?

Dunno, the Copilot mentioned "the older DPSS needed this higher voltage, the newer with direct green diodes are then designed for the same format".
Dunno the exact diode structure, my guess to get the optimum operating point for the coherent "lazing" there are rather high ohmic losses in the diode, so the total voltage is way above the photon energy. The thing is, the coherent generation happens only when the current is above a critical point, below that it is just a plain LED (no coherent amplification needed to form the laser). And that critical point is at rather high current densities, where the ohmic losses in the material are high so cause large parasitic voltage drop.

There are different materials involved, so it could be a blue laser, although needing higher voltage for higher photon energy, may happen to have way lower ohmic losses for the critical current than what is used to make the green laser (regardless if direct green or DPSS).