I found this product on the web. It is a prototype designed by a couple of American cyclists who are now using Kickstarter to find funding to put it into production. They are inviting people to make an advanced payment of $40 plus $10 delivery to the UK. The payment is only taken if they receive funding which exceeds their target.
So for less than £35 you could have a water bottle which holds just under pint of liquid with your front and rear lights built in. To read more and see their video click on this link: aqualight-water-bottle