Hi there
It depends, for how long will be working? or how often it will be returned from sleep ? and what current do you need.
One of the options is to use simple solar cell(picture a) and
build a simple DC/DC converter or use a specialize silicon devices for that(search on web).
Or buy a simple garden solar lamp(picture b)
Inside you will find battery -charged every day with ~1.5V out. , use DC/DC switch-up converter (eg.MAX 1674,MAX1724) to 3.3/5V output.
Current required for LPC2129, hmm it depends from frequency/ active pheriperials/....
For example LPC working on 60MHz , takes ~50/60mA in standard mode.
Using LPC + Zee bee be sure that current consumption may be ~ 160mA less or more.