Cerakote is highly rated.
That said, Eastwood has recently announced a product called Exo-Armour Coating:
According to claims, it's a two-part, high temp, corrosion-resistant, low gloss, air dry coating to protect painted, bare and polished surfaces. In addition, it can be applied by brush, pad or spray. No affiliation and no independent reviews I could find.
Exo-Armour High Temperature Clear Coat
Anyone?
Sherwood