You cam get replacement led ones.The small ones are 4mm and large are 5mm.You can get them in green.The old bulbs have a green plastic sleeve over them.I may try to pull the old bulbs out and try to replace them with led bulbs from Radio Shack.
http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fspecs%2FNEO.htm