I have one up for auction on Ebay at £14.99 + £9 P&P (userid rabpete).
The postage is a killer, so if you can collect from Rugby, Warwickshire then you have got yourself a bargain for £15. My father makes them as a hobby and takes pride in his work.
If you want any advice about making one let me know, it is your cheapest option and should cost less than a tener, maybe even a fiver if you get lucky. Go to your local wood yard and get some off cuts of either 9mm or 12mm plywood. They will only charge you a couple of quid. Get two 75mm hasps and clasps plus two 75mm hinges from Wil