A nalgene bottle will nest in an Olicamp stainless cup. You can then take both the Nalgene and the Olicamp stainless cup and nest both of those inside a Zebra 12cm Billy Pot (without the billy pot's lid).

http://www.amazon.com/Olicamp-Space-Saver-Cup/dp/B0059QHNWS

http://www.bushcraftoutfitters.com/Zebra-Loop-Handle-Billy-Pot-12-cm-zebra-billy-12.htm