Most any automotive store (NAPA, etc.) will have spray paint for headers.
If you want something that will last much longer than header paint, then
do a Google search for a company that does Ceramic Coating in your area and have them Ceramic coated inside and out.
Is Jet Hot Coating company still in business ? They had a facility in Pasgagoula MS that I sent my Fenton headers to but thats been 20 yrs ago. They still look as good as the day I got them .
Rustoleum has new high temp paint that I put on the steel Red's Headers on my '36 coupe a couple thousand miles ago and they still look great. I also have Red's ceramic coated headers on my 36 sedan and not happy with them. They are about 6 years old and beginning to be very rusty looking. Haven't tried much to clean them up. I also have a pair of Dynoflow ceramic headers on a '50 chevy pickup--10 years and looking pretty tacky as well. I don't think the ceramic hype is worth the money. Have yet to be really disappointed with the Rustoleum products. Rod
Is Jet Hot Coating company still in business ? They had a facility in Pasgagoula MS that I sent my Fenton headers to but thats been 20 yrs ago. They still look as good as the day I got them .
Jet Hot is now in North Carolina. My 20 year old FENTONS that they did look just like new. Painting headers is a frustrating waste of time and money - rarely lasts. http://www.jet-hot.com/
Did you bake the paint on before installing them?
I just did mine in VHT black, but I baked them as per instructions in my powdercoating oven first. Haven't fired it up yet, so I hope it works.
I use Dupli-Color High heat 1200. Got it at Napa Auto Parts. I bead blast the manifolds to get them clean and then spray them with the paint. My manifolds still look great after 3 years. I've also had some manifolds ceramic coated. I use Cap's Coating in Fresno, Ca. They do a super job.
Had Jet Hot do mine 5 years ago. They still look as good as day 1. I just couldn't find a spray that would stay very long. Nice thing about Jet Hot is they do the inside as well as the outside.