I've bought some from https://www.meinkopter.de/ (because it's located in my hometown and the guys are connected to a local hacker space) and http://premium-modellbau.de/ (who doesn't sell them as "Suppo" brand, but "no name" - you have to search for the model number like A2208/14 to find them). Flyduino has them too: http://flyduino.net/Suppo-Motoren (but only two at the moment?)
