One company is offering the flag of Hanoi, Vietnam. I don't have any information about this flag, but if you do, please let us know. It is shown as a red flag with the municipal emblem in yellow. Valentin Poposki, 5 July 2012
A vertical flag with this emblem at the top and an incompletely visible inscription in five rows beneath was photographed in Hanoi on 5 October 2010: https://www.flickr.com/photos/montesi/5155915790 [defunct website]. The emblem is obviously not "segmented" as shown in the photo from Superstock. It is actually a stylized representation of a building from the Hanoi Citadel complex, two photos of which, taken from different angles, can be found here: https://www.flickr.com/photos/josvanderheiden/9116622828 and here: https://www.flickr.com/photos/josvanderheiden/9116615940/, the latter clearly revealing the view of the building which was used as the model for emblem. Tomislav Todorovic, 29 June 2014
A photo, taken in Hanoi during the celebrations of 70th anniversary of national independence, can be found here: http://www.talkvietnam.com/2015/09/capital-city-of-hanoi-on-special-autumn-days/ (Image: http://static.talkvietnam.com/files/2015/09/12000-students-participate-to-form-a-living-map-of-vietnam-the-national-flag-the-party-flag-and-hanois-symbol-photo-vna-1731701-1185531307.jpg [image no longer available]).
It shows the participants, dressed in national colors, who have grouped so as to form the pictures of country map, national and party flags and the emblem of Hanoi. Note that full name of the city is replaced here with the abbreviation HN, since the representation of full name would require many more participants, probably much more even than the complete number of those who had formed all four pictures.
An earlier version of the emblem, showing a more realistic depiction of the building, was used on the billboard announcing the 990th anniversary of Hanoi. The colors used were the same, so as to match the depictions of national and party flags with which it appeared. The photo of this billboard, taken on 24 February 2001, can be seen here: https://www.flickr.com/photos/acordova/656075896/ Tomislav Todorovic, 22 November 2015
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