A backpack such as this one can be very useful for a number of things. If you prefer red backpacks, then this should you just fine and it holds seven litres.
From Amazon
CAMELBAK Octane 9 Packs - Burgundy/Hot Coral, One Size
Trekkinn
Camelbak Octane 9l Backpack Red
OnBuy
Camelbak Womens Octane 9L with 2L Reservoir