Sula, no brand name on the control stick. I have found a brand name on the propeller blade, which is kind of difficult to identify since I have not seen the brand before. Here is a picture.
Andres, it's 'SLEIPNER'. They are a very well established Norwegian company, but their bow thrusters are now branded as 'Side-Power'.
If you contact your local Sleipner office or Side-Power agent, they should be able to help you. I think if you could provide them with photographs of the motor as well as the thruster propellor that may help them identify the particular model.
I think you are based in Germany. If so, this is their German website: de.side-power.com