There was no "Italian Brigade". There was a "European Brigade", made up of New Orleans residents who were nationals of foreign countries and who did police work in New Orleans. It was not a Confederate unit. I've never run across a field officer, let alone colonel, by the name of Rizzio. The Broadfoot index to the compiled service records show no Confederate named "Rizzio", let alone "John Rizzio". The closest match was a Pvt. Guiseppe Rizzo of the "Italian Guards" Battalion, European Brigade.
The 14th and 15th LA were informally known as the "Polish Brigade". They did have a lot of "ethnic" Confederates and did serve in VA. If this Sgt. existed at all, he may have been a member of these regiments.