Why was the New Orleans flag altered in NCIS New Orleans?

In the season finale "Checkmate Part 2" May 15, 2018, a flag was flying from a small rod attached to the upper railing outside the building were Pride's bar was located.

The flag resembled, but was different from, the city flag of New Orleans.

The municipal flag of New Orleans is the representative banner of the city of New Orleans, Louisiana. The flag has a large white field that contains three gold fleurs-de-lis and is bordered on the top by a red stripe and from below by a blue stripe. The presence of the fleur-de-lis, a stylized depiction of a flower and a traditional French symbol, demonstrates the city's French heritage and strong ties to France.2

https://en.wikipedia.org/wiki/Flag_of_New_Orleans3

https://en.wikipedia.org/wiki/Flag_of_New_Orleans#/media/File:Flag_of_New_Orleans,_Louisiana.svg4

In the episode the white area, by far the majority of the flag's surface, was colored yellow instead of white, and the yellow fleur-dei-lis were colored blue instead. The upper and lower stripes might have been colored differently from in the New Orleans flag.

The production company should have been able to order a New Orleans flag of the size seen in the episode and have it shipped to the filming location for less than $ 100.00 total. So why go to the trouble of making a similar but different flag for use in the episode? Or are there flags like the one in the episode for sale somewhere?