You can lease a new car in Mauritius, but you typically have to make an initial payment of at least 25%. I have heard that some require a 40% payment upfront. Even "buying" a car (new or used) has the same upfront payment requirements as well assuming you aren't going to pay for it outright.
The "lease" is not your typical lease either in that you monthly payments are just as high as buying and when the lease is over, you have essential paid off the entire value of the car. There is no "trade in" option for another lease vehicle after a couple years as is common in other countries.
Insurance will cost you typically anywhere from 3-5% or more of the purchase price annually and fuel is another big cost. You will spend at least 5,000 - 6,000 rupees per month on fuel at a minimum. This figure is assuming just a short daily commute (10-15 minutes each way), a small size car and only a small amount of driving in the evenings or on the weekends.
This figure has been my average for the past 3 years for my small Toyota Vitz. Obviously, you're mileage may very and it goes with out saying, but I'll mention it anyway, the bigger the car / engine, longer your commute and the more you drive the vehicle, the more you will spend on fuel.
Despite what Yud said, I actually think there is a decent selection of trucks, SUVs and cars in Mauritius. Toyota, Mazda, Ford, VW, Nissan, Honda, Kia, Hyundai, Mitsubishi, Suzuki all have dealerships and offer trucks and/or SUVs as well as various sized cars. Isuzu, Chevy, Jaguar, Mini Cooper, Renault, Citroen, Alfa Romeo, Proton, and Subaru are all represented on the island as well.
You can even go for a Range Rover, Porsche Cayenne or BMW X6 or something by Mercedes or Audi if you really have money to burn. Great Wall Motors on the other hand also offers a decent truck from China that is reasonably priced and supposedly has decent reviews from the people I know that have one.
You won't necessarily have an endless choice of colors or options to choose from when you go to any dealership in Mauritius so you may have to be flexible to some degree unless you are not picky. Otherwise, you may have a long wait in store to get the exact model, color and option combination you want.
Personally, unless you actually need the extra cargo space or are planning on doing a lot of driving off the paved roads or have a large family and are looking to get one because of safety concerns, a large vehicle in Mauritius can be a slight disadvantage at times given the difficulty to find suitable parking options as well as Mauritius having narrower roads than what you may be use to as well as the extra cost to run and maintain them.