The idea of a milk protein fibre piqued my interest. Sure enough, you can apparently make a yarn out of a blend of casein and acrylonitrate, which apparently is silky smooth and has anti-bacterial properties. Apperently, the idea of making clothes out of milk fibre is not even new - they were around decades ago, but fell into disuse when synthetic fibres came along.
Bamboo fibres too, are supposedly a good starting point for fibres so what do you know. A couple of links, for anyone interested - but milk protein fibre sounds tough to make.
http://exchangingfire.wordpress.com/2011/02/25/what-is-milk-fiber/
and something on bamboo fibre
http://www.bambooclothing.co.uk/why_is_bamboo_better.html
If you are seeking suppliers of such material, your best bet would be to search for chinese textile exporters as a starting point, i would imagine.. sounds interesting!