I use a Mountain Equipment Co-op (MEC) brand "thermos". It is stainless steel. I've had it for over 10 years and it is awesome. I don't know if they still sell them, but the one I have (actually 2 if I include my wife's) is excellent quality.
Edit: Similar to this
http://www.mec.ca/product/5029-809/m...acuum%2Bbottle