I know there may be language barrier but you might do well to try a german forum called blasted.de, or else do a search for french nerfing communities, even try facebook. It'll be much easier if you link up with a community in your area that's already done the hard yards.
As far as I can tell pretty much every region has their own range of plastics, singapore has the truly excellent singaplastics, australia has keyplas piping, (at electrical supply stores) and a range of metric PVC and other poly conduit (available at hardware stores). One thing though that's been pretty consistent across regions is the availability of brass at hobby shops, so if you're truly stuck for barrel materials just fork out a little extra for brass tube. With a clean barrel and good dart fit brass performs better than just about anything.