I live in Japan and milk is sold only in cartons here. I take milk to the fridge at work. I currently put it in a black plastic bottle with black cover but it stinks like it is off after only a few days. The milk is fine as far as I can tell. I doubt there is food safe plastic bottles here. I carry by bicycle and the bar fridge is small and at times very crowded as it shared so spillage is a great risk. What is the best solution? I use the milk  for adding coffee and cocoa- I may have one drink or many drinks- depends on how sleepy I am that day. I buy 1 litre cartons as I am poor but I couldn't drink 1 litre at work in a week even. The main milk is always fine. 
The key thing is that you empty and wash the container regularly (ideally daily, but at least every few days). If there is a bad smell that is a sign that something is wrong; most likely some milk remained somewhere like a screw top or drops on the lid, which has gone off in some way. Any bottle sold for drinking water should be food safe in terms of its material, so I would be very surprised if you cannot find anything. However, I would try to find a bottle which:  is easy to clean completely, so no complicated closing mechanism or built-in drinking straw. will provide reasonable insulation while the bottle is out of the fridge, for example a thermos bottle (which uses vacuum in the walls to insulate the contents).  Anything suitable for carrying hot coffee is likely to work well for your needs, in case that's a useful way to search. 