One process worth mentioning is treating stainless steel with IVD - ion vapour deposition - to give an aluminium coating. You can then anodise it in the same way as aluminium. This process has basically replaced cad plating of SS and can be applied in greater thicknesses (up to several mils thick), which would surely help the thin mesh of these grilles. IVD also provides galvanic protection for these alloys allowing dissimilar metal usage. Only downside would probably be cost of application.
Quote from Dow Automotive:
Topcoats, such as paints, sealants and lubricants improve the performance of the underlying basecoat. For example, topcoats are used to improve corrosion resistance, improve erosion resistance, or change the coefficient of friction of a finish system. The application and successful performance of any topcoat is dependent on basecoat qualities such as coverage, uniformity, and adhesion. IVD aluminum is characterized by excellent adhesion, coverage and uniformity. Evaluation of the penetration of an epoxy primer into the columnar structure of an IVD aluminum sample by scanning electron microscopy indicated a skeleton of primer penetrating into the structure. This feature considerably enhances topcoat adhesion. Both IVD aluminum and cadmium are soft coatings that are not particularly well suited for erosion resistance when used alone. IVD aluminum outperforms vacuum-applied cadmium in resisting abrasive forces and diffused nickel-cadmium when subjected to an erosion/corrosion environment. Economically, IVD aluminum can be applied thicker than cadmium and, therefore, is more abrasion resistant than cadmium. Also IVD aluminum is well suited to accepting topcoats of abrasion-resistant materials.