It's doable.
1. Check local computer stores. (Fairly common, used for inkjet printers, & other items). 🙂
2. Special order from Apple, or online. 😱 🙁
3. Cut the US end off, and wire a UK end on. Just make sure to observe polarity. (This is very easy, but may not be pretty, depending on your wiring skills). 😱 😉