I found a replacement light for my hitachi saw at lowes, it was in with the appliance bulbs. I took the old one along to compare.
Mine lasted about 5 minuets before burning out, well actually shaking the pieces loose. The bulb should really be a rough service type. I couldn't find one (ok, I didn't look that well) so I just modified an adjustable desk lamp to fit near my saw, way better light then the little light on the saw.
MrsN