As you're not putting milk in (and not effectively blunting the flavour), you need to take the tea bag out much sooner. I've also treated myself to decent coffee, given that I'm not spending out on anything else... Give Earl Grey a crack too (but don't stew that, either), and if you live in a crappy water area like I do, you will notice the difference using filtered water.
As you know, fruity teas are out, not least because they may, um, have fruit in. However Twinings do a rather interesting range of 'Green tea and...' and sling in a bit of flavour. Now, they don't seem to do any harm to me, I'm assuming there's not enough 'and...' in it to affect ketosis. However this is no general claim that they are diet friendly! I occasionally stick one in a mug and keep topping it up with hot water over the course of the evening just for a change.
The occasional mugful of Marigold reduced salt bouillion will do too.