Hi Yves, yes PVC pipe and fittings are hard to find up here. However if you can find a plumber or a plumbing shop near you they should have it. Also check out Home Hardware, they may not have the parts in stock but can order them in.(stocked in their warehouse) The only drawback w/HH is that you'll have to pay for a 10' of pipe unless they are willing to sell by the foot.
I've built my reactor out of ABS and so far no problems other than it's too small. ( used 1-1/2" vs 2", causing the water flow to be too fast for proper absorbtion of the CO2.)
PEX is a high pressure flexible line that uses crimp-on fittings vs glue and yes it will replace CPVC/PVC eventually ( for water supply) as it is a lot easier and quicker to work with.