Why is it difficult to find pvc pipes in europe?
They don't have the DIY market as it exists in the USA - many homes are older and there are a ton of regulations regarding who can build what, when and where. Also it might not be legally allowed by law to sell it directly to an end user. The fact that it has PolyVinyl Chloride is probably a regulatory issue but I do not know that for sure.

I know that Industrial supply companies do have them as a previous European employer of mine built machines with PVC, given you are mentioning France too that side of Switzerland .. I am thinking Germany might be some distance. 

If you are desiring to weld it together make sure it is all of the same type as US and European PVC do not weld together - I am not talking glue together - I am talking welding.

Also you might want to check with Local Laws as to whether or not you can even make that toy 'legally' .. European Laws can be strangely different and somewhat constricting in comparison to any one who has lived in the US, for example the Hitler salute can be done in the USA but not in Germany and there are plenty of other such laws besides this more well known law.

Bonus:
Wood is the best alternative material in Europe.

PVC PIPE Suppliers in Europe