Formal:
* Le balai de Harry: This is a direct translation of "Harry's broom" and would be the most accurate but a bit clunky.
* Le balai magique de Harry Potter: This is a more descriptive option, using the magical aspect of the broom.
* Le Nimbus 2000: This is the specific name of Harry's first racing broom, which is widely known.
Informal:
* Le balai d'Harry: This is a more casual version of "Harry's broom".
* Le balai volant d'Harry: This is a playful way of referring to Harry's flying broom.
You can also use the French name of the broom model, such as "Nimbus" or "Firebolt".
Ultimately, the best option depends on the context and the level of formality you want to achieve.