[Roger Bamforth]

I bought this one

http://www.amazon.co.uk/gp/product/B00CRXB9US/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1

It works fine. I liked that fact that a) it has an on/off switch and b) it's black so doesn't stand out like I expect all the blue ones on Amazon would.