Ace Rust Stop Enamel has a tintable base. I picked up a gallon of Mopar's Tahitian Gold for the Serious Satellite project. I went with the non metallic base, but I'm going to try a quart of Tahitian Gold metallic base after I lay the non metallic down.

At two different Ace stores in the Dayton area I've been in they can mix up the custom colors.

I matched up the paint I wanted with a paint chip. I actually had to go to Lowe's to matchup the paint from 1974 with a chip of similar color, then took it to ACE and they mixed it off of that chip. Pretty easy. And cheap.