Hi mate, welcome to the forum!
There are plenty of specialists on the forum who supply all kinds of cosmetic and working parts for (Cougar Store, Tarmac Sportz etc), If they dont have it, its always worth asking them where the part can be found.
As for another site, I looked on eBay for ages when I was looking for my car. In the end mine was off of Auto Trader but eBay does have a lot of Z's for sale. Its also worth mentioning there are plenty of new and used parts for sale on there.
Hope this helps in some way mate.