If you've still got the insides to a spare key of yours, then this is how you do it
Flip Key Conversion
This is the flip key I bought: ebay Link
It was the only one that looked decent, and came with a Toyota logo. I've had others and they feel cheap, but this one's decent quality.
1. Open up your old key (a single screw by the blade will allow it to pop open), and remove the internal fob. This fob contains the buttons, the battery and the chip, all in one assembly.
2. Using a scalpel or a very thin knife, carefully score the join between the plastic and rubber top to break the seal.
3. Peel back the rubber, and you'll see the black responder chip in the corner.
4. Inside your new key, you'll notice an area to put it.
5. I put a tiny blob of blue tac in first to stop it rattling, then placed the chip in this gap
6. Using 3-4 tiny blobs of superglue, re-seal your key fob that you opened. Then, place into the new key housing.
7. Re-assemble the new housing. You have to place the button, key and the spring into one side, then wind it with the other side of the housing - then clip it down. You'll figure it out. You might also notice the buttons are slightly sunken in - this is normal, and just its design.
8. That's it! Get the key cut for around £5 and you're good to go.
When getting your key cut, Timpsons won't do it for you. They used to, but are now not allowed to cut Ebay keys as people blamed them for ruining the key, when it was just badly made. Go to an independent cobblers and they'll do it for you for a couple of quid.
So much better than the standard key.