Hi Terry
The key thing when looking for parts is to start with the Renault part number (and the oval plate number) - it makes the search much easier. If you have a Renault number, there are websites that'll give you other manufacturers' equivalents.
Although there are plenty of specialist companies in France, Germany, Spain and Italy, you'd be surprised at what you can still find in the UK. If you have a Spanish connection, there are lots of R4 parts on Milanuncios.
Which parts are you looking for?