Below is a list of suppliers Fred Russell, Bill Gehring and Doug Breithaupt have used safely and successfully.
Ebay: Diecast & Toy Vehicles Alfa Romeo
Toy Fairs: Regional toy shows are an excellent source of a wide variety of models. Prices are usually good and always negotiable.
talesoftoycars.com Since 1997, Doug has produced Tales of Toy Cars, for the past 10+ years as a daily Facebook blog. This has been the second most effective way in which my collection has expanded. Feel free to contact me at firstname.lastname@example.org or 206-323-0624.
Antique / Thrift stores: Sadly, some car collections end up in antique stores as the family gets rid of too much stuff. Some fun jewels can be found.
Europe: Most cities and towns in Europe have miniature car stores. I research them and create a list prior to my travels so I do not miss them.
Retail Stores: Target, Walmart, Fred Meyer, Toys-R-Us, Supermarkets, drug stores and other North American retailers. (Typically 1:55-1:76 scale range)
Replicarz: https://www.replicarz.com/ Coming out of Rutland Vermont. Very good mix of cars and they have a few cars made just for them.
CMC-USA: https://www.cmcmodelcarsusa.com/ HQ is in upstate New York, with cars engineered in Germany, and manufactured in China. Very high quality, mostly 1:18 scale, and mildly expensive.
Eautomobilia.com: https://www.eautomobilia.com True European depth of miniature cars but located in Vancouver BC. Storefront: Wilkinsons
Alpimodel: https://www.alpimodel.com/ Located in Italy and carries a huge variety of Alfas and other Italian cars.
Mondo Model Cars: https://www.mondomodelcars.it/ Like Alpimodel, located in Italy and has a great selection of Italian cars.
Amalgam: https://www.amalgamcollection.com/?currency=USD Coming from Germany, these are extremely amazing 1:8 scale and expensive.
DMW: https://www.diecastmodelswholesale.com/ Located in near Los Angeles, CA, they have a good variety and often reasonable prices.
Diecast Legends / Grand Prix Models: https://www.diecastlegends.com/ Located in the UK, they have an outstanding level of quality, and mix of cars.
Laudoracing-Model: https://www.laudoracing-models.com/en/ On the SE border of France, these people make great 1:18 scale cars ar very good prices. The doors and hoods don’t open, but the exterior details are very good.
Mint Models: https://www.mintmodels.com/ Located in Albany NY, they have a wonderful mix of everything from Corvettes to Trabants.
EXOTO: https://www.exoto.com/ Great miniatures are reasonable prices. Owner may be overworked so if any purchase goes wrong, its tough to get it fixed.
ITALERI: https://www.italeri.com/en Almost exclusively model kits but a number of great Alfas (P3, Alfetta 158, Giulietta Spider, 179C, etc…)
MiniWerks: http://www.miniwerks.com/ Custom, high quality miniature cars. High priced but worth every penny. Alfas at times.
Mini Garage: https://minicargarage.co.uk/ Out of the UK, their focus is on 1:64 scale and they have some fun items.
CAR Model: https://www.carmodel.com/ Located in Italy, they mostly sell new, but also have some second hand rare cars at times.