Cheapest at Amazon seems to be about £35.

In theory you could make your own. Just use a heat source like an incandescent lightbulb (if you can still find one!) and a small box fan. It doesn't need to be transparent - use an old kitchen cupboard carcase, and fix up some battens on the inside to use as drawer rails. For the drawers, just some plywood with a square cut out and some mesh attached to allow for airflow. Of course, if you had to buy all this - it would be easier to pay the £35 - but if you have this stuff around, or have the need for higher volume - this will work. Similar contraptions are used to dry biltong.