Here’s a modern take on an old solution, though mountain bikers will consider it a bit old-fashioned to carry a drink round in a bottle cage. Ever-shrinking batteries mean you don't even need a cage for your lights any more.
This Easton made cage is constructed from a single piece of carbon fibre and weighs just 38g. Roadies looking to shave grams will like that, though Easton's cage faces stiff competition from any number of carbon fiber cages, some even lighter.
It looks great, but is pricey.