Topman/topvrouw for sure, used a lot, especially in the media. Bestuursvoorzitter is specific. Bestuur = board, voorzitter = chairman, so you can use it for companies which actually have a chairman of the board. However this probably isn't the best word to use whenever the actual structure of a company is unknown or not relevant.
Changes the meaning in Dutch sightly, but if translating from English both probably should be accepted. Without 'een', it implies it is your (main/sole) profession, with 'een' it could be something part of your character. Which of those two would be a (more) 'true' entrepreneur depends on values/outlook, so it is tricky to interpret.