found these great for a caravan was £5
Rid your home of damp, odours and condensation with the Minky Damp Guard Mini. Measuring only 18cm in height, this small moisture absorber uses tablet technology and adjustable vents for optimal moisture absorption. A spout is built in for easy pouring of accumulated moisture.
Universal for both tablet and granule use, the Minky Mini has a 75g refill system with tablets are available and sold separately.