Best bet is eBay, search for ABL (Armee Belge - Belgisch Leger). You can find quite good deals there, although a lot of the auctioned camos are quite worn out.
Even for us Belgians it's getting more and more difficult to get new jigsaw camo. I have heard from a militaria dealer that Seyntex, the company that produces them, has been banned by the gov't from selling to civilians. Whereas even a few months ago a new Belgian camo suit went for around 50-60 euros (the build quality is awesome by the way), by now they are going for 170 euros, if you can find one.
More info and detailed pics of the Belgian camo can be found here:
http://www.airsoftcanada.com/showthread.php?t=38280
Hope this helps.