The Natural History Museum has some amazing gift ideas, and two of them include re-usable travel mugs.

There's one with a safari theme with different wild animals on it, for £12.00

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And there's the Bamboo Re-usable Dinosaur Travel Mug also for £12.00:

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Both travel mugs are a Natural History Museum brand, too, and dishwasher safe :-) 

Take a look at all the mugs available from the Natural History Museum here.