It varies.
Thermos brand thermos.
Widemouth white nalgene.
Recycled pop bottles. (cheap, replaceable and reasonably tough.
I have found dairies here selling milk in exceptionally tough plastic bottles.
Here is a link showing a picture.
http://www.saputo.ca/dreamsv2/Product.aspx?id=4They come in half liter size which is about a pint,
They work very well too.