There are hybrid bikes that come with adjustable stems. They have a pivot on the the steering axis. Usually they break and are crappy and are a one time only adjustment. Either learn to ride your uncomfortable fixed gear just like everyone else that cut their bars really short, has a frame that is too short for them and a drop stem, or stop buying parts that are 'track' and get parts that work for your needs...aka road drops. If you have brakes, you have at least 4 hand positions. You really wouldn't want to 'adjust on the fly' something you need to control your bike anyway.