Legacy's Diecast Zone auction:

https://www.diecast.org/diecast98/html/asp/auction/auction.asp

Collectors Weekly on line auction:

https://www.collectorsweekly.com/model-cars/diecast/auctions

Craigs List (no relation - LOL)

Facebook: F1 Model Sell, Swap or Buy site

Maybe Auction Zip:

https://www.auctionzip.com/