Panasonic Lumix DMC-G3

I have a Panasonic Lumix G3 camera which came with a 14-42mm lens. Although this is a fantastic lens, i require something around 45-200mm so i can zoom in. The Panasonic lenses are so expensive and i have heard that you do get 'Sigma' lenses for cameras but i've only seen them for Sony, Nikon and Canon. Does anyone know where i could find a lens?

Sigma only do lenses with the following mounts - Canon, Nikon, Pentax, Sony.

Your camera uses the micro four thirds mount that it shares with Olympus. It is a fairly new system and uptake has been slow so no 3rd party manufacturers make lenses yet. You are limited to Olympus or Panasonic lenses.

There's a selection here
http://www.parkcameras.com/c/168/Micro-Four-Thirds-Fit-SLR-Lenses.html

An Olympus 40-150 (80-300mm equivalent) is only £250. That's not that expensive for a lens to be honest.

Another option would be to buy a Four Thirds to Micro Four Thirds adapter and buy a 2nd hand Olympus 70-300mm lens for example.