You might inquire at a metal plating shop near you: Can black anodized aluminum alloy be overplated with a chrome/nickel finish?
Quick research indicates you can chrome plate aluminum:
"US Chrome is able to hard chrome plate on many different surfaces including
Aluminum,
Titanium, Inconel, Brass, Copper, Steel, Nickel Alloys, Cast Iron, Bronze and many more exotic metals." Whether the anodizing has to be etched off, etc. is not detailed.
More quick research reveals:
"An article on the coating website Anodizing, Plating, Powder Coating, & Surface Finishing “Changing Anodizing Color ? ( 2005 )” says one needs to strip dyed anodized aluminium between colour changes. According to the article, one cannot simply anodize over dyed anodized aluminium."