In alphabetical order:
Centre for the Understanding of Sustainable Prosperity
Green Economy Coalition
https://www.greeneconomycoalition.org/
Institute for New Economic Thinking
https://www.ineteconomics.org/
International Society for Ecological Economics
London Mathematical Laboratory
New Economics Foundation
OECD New Approaches to Economic Challenges
Promoting Economic Pluralism
https://economicpluralism.org/
Rebuilding Macroeconomics Network Plus
https://www.rebuildingmacroeconomics.ac.uk/