Buying a cheap map case is a complete waste of money. In fact I think that the word has at last got out as I am not even sure if you can get those rigid plastic ones that would split on the first or second use any more.

There are two types of map case that are both very good. One is made by Ortlieb and one by Silva. They appear to be made out of the same sort of material. Over the last decade or so we have purchased a number of both of these makes and have never had a problem with leaking.