How to find paint for my old car?

Generally I'd describe the color as gray. I found the paint code 249 atop the front driver-side strut tower on the plate there. According to Duplicolor's web site, 249 is "Liquid Silver Metal". However, when I tried to find their paint number, they say they don't carry that color. So I'm wondering how I'm supposed to paint my rusted out fender and hood that I'm replacing with used parts (but in better condition and also in a blue color). I figured on sanding down the replacement parts, especially the rusted spots, a bit of bondo to make for a smooth surface, prime, primer seal, and then paint - but I can't find the paint. The auto shops that I've stopped at all carried Duplicolor (yeah, those tiny palm-sized cans) but Duplicolor doesn't carry my color. Argh!