George Zimmerman, who shot and killed an unarmed black teenager in 2012, is selling his paintings of the Confederate battle flag "in honour" of a Florida gun store owner.
The Florida Gun Supply website says he is raising legal funds for himself and the store's owner, who in July declared his business a "Muslim-free zone".
The Confederate battle flag is seen as a symbol of slavery to its critics.
But its supporters today say it is an important part of southern heritage.
Florida Gun Supply owner Andy Hallinan said he teamed up with Mr Zimmerman, who was acquitted in 2013 of killing black teenager Trayvon Martin, to sell copies of his Confederate flag artwork.
Mr Zimmerman later tweeted about his reason for painting the flag.
"I painted the confederate flag backed by the American flag because I believe that anything can stand with the American flag behind it."
He added: "My confederate flag painting also represents the hypocrisy of political correctness that is plaguing this nation."
'Splitting the proceeds'
A post on the store's website said Mr Zimmerman painted it "in honour" of Mr Hallinan "for being a true patriot and leading the country into a better, safer America".
Andy Hallinan courted controversy last month when he announced in a YouTube video that his Florida shooting range was closed to Muslims.
Mr Zimmerman said he decided to paint the flag after hearing that the Council on American-Islamic Relations was taking legal action against Mr Hallinan.
At the time, Mr Hallinan said his decision was inspired by the Chattanooga shooting, which was carried out by a man born in Kuwait who spent several years living in the US.
Copies of the painting are selling for $50 a piece, each signed and numbered by Mr Zimmerman. It is unclear how many copies have so far been sold.
Mr Zimmerman's last painting, which features a blue American flag with the words "God, one nation, with liberty and justice for all", sold on Ebay for over $100,000.
His acquittal in 2013 stirred fierce debate on racial profiling and self-defence laws in the US.
It also helped spark the #BlackLivesMatter movement and continues to be a rallying cry for civil rights campaigners.
There has also been a backlash over the Confederate flag in recent months, after the man charged with killing nine black people at a church in Charleston in June was pictured holding it.