Where to get TTI Headers Recoated?

if you want ceramic that will last.
It costs no less, generally more, but you can have ceramic melted onto the headers instead of having it applied in a polymer binder.
Its an industrial process: zirconium dioxide (with ytrium?) applied using either open of plasma flame. Might find a local place that's willing to do your headers.
Otherwise, there's only one place in the US that advertises specifically for automotive aftermarket. That's Swaintech. They call it white lightning.
Swaintech makes a big secret out of it, but you can go to Zircotech's website (UK) and read about the process.