Ah thanks, that's the kind of thing I need.
Now looking at: NJM2870F48-TE1#-ND 4.8V, 150mA (-0.7 = 4.1v)
But now I can't seem to find the right solar unit. Lot's of things at DigiKey orbiting my specs.
cost < $5 @ 10 units
vMpp around 4.5v-7v
But the current can be quite low. I think even just a few mA would do.