Thanks all for the suggestions... I was on a site earlier today to pick up some Klean Kanteens for the kids and picked up this guy for myself:
http://www.littleacornstomightyoaks.co.uk/klean-kanteen-wide-insulated.php

going to give it a shot... not expecting too much. But it should be leak proof!
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"One should not increase, beyond what is necessary, the number of entities required to explain anything"
William of Ockham (1285-1349)