Alternative sun light?

Okay, so my outdoor plants are doing rather brilliantly , but there has been very little sun light as of late (melbourne weather ) so i was just wondering if there is any kind of light bulb i can chuck in my lamp to give the plants a bit more of a boost?
Ta, Chris.

A lightbulb outside? why would you do that?

even on cloudy days youd be surprised the amount of light your plants are actually getting no need for extra light