I get mine from a german company on ebay, there stuff is very well made. I got some brake lines off them and they have titanium banjo fixings and a life time guarentee, I did pay for the privalige though, but next to goodridge the goodridge look cheap and nasty! they make cable for my rs 125 and they are honestly, much better than the ones from aprillia. But if your worried just go to aprillia.... Type in "aprilia genuine parts" on google and use one of the aprilia dealers there. Sometimes you can wait a little while for bits to come through but they always get there in the end.
Worth checking if you have got the cable linkages all set up corrcetly because I rarely have to replace a cable and I only use the ones off ebay.