they are there Sunking. Usually out of two pages of auctions there will perhaps two. Depending on the plane of course. A P-51 for sure, a P-39 not as likely.
Sadly Armour Models no longer make thier 1/48th scale die-cast aircraft. They got bought by the Franklin Mint.
I liked thier models. I did buy P-47 in a 57thFG scheme as well as a P-38 in McGuires from Bhodi. He has a company, or works for it anyway, in Florida that helps to restore old aircraft. They sold these also. You can find them on Ebay now but thier prices are up beyond what they had been when regularly available.
And also to echo what Gofaster said. You can pick them up at a hobby shop or even during a Modeling clubs "open house" if you have them in your area.
Westy