They're called Duckheads and are about £4 on Amazon or from the myriad of phone shops in Petticoat lane market. The Amazon ones are perfectly fine IME.
I have a bunch for different countries so when I travel abroad I just grab the relevant one instead of a full UK-EU power adapter.
Anyone know where I can buy this bit of an apple power adaptor?
Apple store told me to buy an ipad charger and take the bit off -- at £19 that feels like a waste of money and plastic ...
Amazon has some asian ones but they have poor reviews ...