Hope this will be of interest to someone.
Just found this on the WH Smith website. I'm sure they were originally £24.99 in the shops. They are now only £3 and you can get them delivered free to your nearest WH Smiths store.
These are for sale in store as well, but the price is higher (it's a different company that run WH Smiths online, apparently!)
Science Museum Signal Lights Create secret messages using combinations of coloured lights. Red, green and blue lights are for sending secret messages. There's a handy torch for undercover work and a belt clip keeps your coder close at hand.
Blue, black and silver