For anyone looking at hiring a motorcycle in eastern France/the Alps area, I can recommend this company - 'The French Ride'.
They are based in Aix les Bains, about halfway between Geneva and Grenoble. They hire out a range of modern bikes, I guess 20-30 to choose from, and also hire most riding gear.
I enjoyed a 3 day hire from them in September 2023, and was impressed with the professional and efficiently run business.