I first bought this travel tea tumbler from David's Tea last year.

Its perfect for loose leaf tea and I love that I can pull the the infuser up out of the water before it gets too strong.
It has a double insulation and keeps my tea warm for a couple of hours.

Its really durable, I put mine in the dishwasher and have dropped it a few times and it didn't break.

I bought another a couple of months ago, now I have one at home and at work.