[Ceretrea]

If there's no other option then a tank would be fine. If you can't attach a water bottle you can give chunks of cucumber or carrot soaked in water although not too much as, depending on where he's from, you don't want to introduce too much veg too soon. You can still velcro a small water bottle onto the inside of a plastic tank so that might be the best solution.

You could always grab an exoterra faunarium from Pets at Home and cable tie a water bottle on it's side on the roof.