Most of the parts that I needed for my Fiat 850 project were sourced from the internet. Google is your friend when you know what you need. Parts manuals are ideal to find parts numbers. Have a look in my "Manuals" menu if you don't have a parts book for your car. There's a good choice of books available for download.
I bought my parts from:
- Private sellers that had to end their projects because they were short on time or space. And don't forget WAF as a reason for having to sell parts!
- Companies that specialize in NOS or newly made parts. There are quite a few of them around in Europe and I have bought from all of the following:
Martin Willems (The Netherlands)
FDRicambi (The Netherlands)
Holtmann & Niedergerke (Germany)
Scuderia Topolino / Abarth-online (Germany)
Cicognani (Italy, rubber parts only). This company uses the original factory moulds to fabricate rubber parts for many Fiat models. Not cheap, very high quality!
I can highly recommend all of these companies; acceptable prices and good support when you are unsure of what you need.