You can get the rules here:
http://www.dakkadakka.com/dakkaforum/posts/list/458652.page
There should be an entry in the list for Dark Future. As for the materials itself, the game is long
OOP and as far as I know, is not remade so if you want the actual game board, templates etc then your only recourse is to get a copy from Ebay - I managed to get a mint copy for £40 about 6 months or so ago so they do crop up from time to time.
Unfortunately, like Man O War, this is one of those games that while being long since
OOP,
GW won't license the game out or relinquish copyright control over it so they are effectively left to fade into memory. It would be nice if they would license them out to
FFG or similar so some new people could have a look at playing these old (and fun) games.