I would try a paint shop, or a parts store that sells paint (like Carquest). I have had them mix paint for me before, and you can look at it before you take it in case they don't mix it right (that happened once-they just had the color a shade off, but it would have been a screaming difference on the truck!)
www.paintscratch.com, you can get it in paint pens, traditional touchup bottles with a brush, spray cans or in regular paint cans. Yes their prices may be a bit high compared to AutoZone but, you get what you pay for. My paint is Laser Red which is a 3 stage paint and it matched perfectly.