Just had a thought...
Most people don't know this, but all these Rustoleum type paints are Alkyd enamels...this type of paint has been around since the 1920s when Du Pont invented it as a (more expensive) alternative to nitrocellulose laquer. The new paint was called Dulux, and was a "synthetic" paint because the alkyd resin base was...well, synthetic. Dulux was used as OEM paint on a lot of cars in the 50's and 60's...the Du Pont paint chips for my '60 Olds list numbers for both Duco laquer and Dulux synthetic enamel.

You can still buy synthetic enamel at most auto body supply stores. It's slowly being phased out...they sell a lot more acryllic enamel, but it's still sold by many manufacturers as a "budget" line.

If there is a color you just HAVE to have, you could probably just go to the nearest auto paint supplier and have them mix up a gallon of whatever it is you want. Price is proabably around $50 a gallon...more than Rustoleum, but you have a much wider choice of colors. The exact forumula will differ from Rustoleum, but the basic chemistry is the same. I honestly don't see why it would go down any different than all the other alkyd enamels we've been using. Everone says not to even try this with a metallic color, but I'm half tempted to get a quart of something metallic just to see what would happen. Might look horrible...who knows. If I ever have an extra $20 and some spare time I'll try it .

Anyway, just a thought. And if anyone makes fun of your paint, just tell them it's a synthetic .