I found this at Tesco Extra Milton Keynes. Car section.
Normal white label, probably national price.
Good reviews at Amazon at £7.53
Description taken from Amazon:
Pingi dehumidifier eliminates moisture from vehicles, the home and other enclosed spaces
Makes for safer driving by keeping your windscreen clear
Re-useable with a fast regeneration time, just 6 minutes in a microwave
Coloured patented indicator lets you know when Pingi is full
Absolutely safe to use around children and animals