Where can I find a good Executive Coach?
As a starting point, you should aim to find a certified coach.
Among others, here are the two most internationally recognized certifications:
ICF (International Coach Federation) and
EMCC (European Mentoring and Coaching Council).
These organisations will provide a list of Executive coaches.
A Certification does not indicate a coach's suitability towards your needs – A certification demonstrates the experience and seriousness of a coach. Multiple other soft skills are important to make the best of your coaching journey.
For instance, certain coaches who have previous experiences in different fields will provide different flavours of coaching. A coach with a creative background will be different from one with a Human Resources or Finance background.
You should consider a minimum of coaching experience for a good Executive coach: 3 years seems to be a good start. The coach may be able to share some successes with you so that you feel more comfortable working with them.