According to the organization's website (which, coincidentally, points back to the Wikipedia article about the organization), Diplomatic Mission Peace and Prosperity (DMPP) is an international lobbying organization accredited in the UN, the US, and the EU. The organization was founded by former US Ambassador Richard Holbrooke as a peace mission in the Balkans and around the world. "Diplomatic Mission Peace and Prosperity works for the creation of more powerful lobbies with world personalities in support of Balkans’ democratic developments, of those of the countries under development, according to the UN’s principles and American democracy. The activity of DMPP is extended in Albania, Kosovo, Montenegro, Macedonia, Italy, Israel, Turkey, France, Belgium, USA, South America, Africa, Australia, India, etc."
There are several photographs on the Internet showing meetings of DMPP members with world leaders, with the DMPP flag displayed in the background. I have attempted to gif the flag based on those photographs. The flag of Diplomatic Mission Peace and Prosperity features the organization's seal in blue and green centered on a white field.