Mauritius is comparatively small and the people are rather flexible. If you need a car for long stay you do not necessarily need a car company in Flic en Flac directly.
Within the last years we used to work together with Honey Car Rental Ltd. They are in Grand Gaube but offer services for delivery and pick up. Just have a look at:
Just ask for Mr Daby. He is credible, makes good prices and the cars are in a top condition.
All the best for you and take care