image found by Valentin Poposki, 30 September 2023
Here are some flags that are made and offered by Flagmaker & Print, claiming that they are unofficial flags of four independent cities and one municipal city in Vietnam. I found them as links from here. The images from that website include Can Tho City (Independent City), Da Nang City (Independent City), Hai Phong City (Independent City), Hai Phong City (different image from Wikipedia), Ho Chi Minh City (Independent City), and Thu Duc City (Municipal City, part of Ho Chi Minh City). Valentin Poposki, 30 September 2023
This one is a modification of the flag of the Hai Phong football club. I cannot tell if the model flag has any official status, but is widely used by the club supporters, with lots of photos found online. Tomislav Todorović, 1 October 2018
image found by Valentin Poposki, 28 September 2019
These days I'm searching through some Vietnamese websites looking for anything interesting. I didn't find any flags (yet), but I did make a small, nice collection of Vietnam Provinces emblems. Valentin Poposki, 23 September 2019