There is a fairly simple solution and that is to have them powder coated. Powder coating is heat resistant (at least to the limit of brake temperatures), extremely durable, and the colors available are nearly infinite.
My recommendation would be to find a Powder Coating operation near you and have them give you a quote.
Depending on your DIY-ability, Powder Coating at home is absolutely possible. All you need is chemicals to strip the existing paint (or have them media blasted), a powder Coating gun from Harbor Freight or Eastwood (less than $100) and your toaster oven.
Go on YouTube and search powder Coating Brake Calipers. There are also various posts on the 6 forum where people have had theirs powder coated. Look it up.
Brake Caliper Powder Coating Video.
L