I would be amazed if such a thing existed.
When I have rented cars, they told me that its such an alien concept to Argentines that there are only a few thousand rental cars in the entire country.
The idea of leasing cars is predicated on companies paying for it- because, in the USA, and the UK, where its popular, its usually much more expensive than outright purchasing the same car- it is usually only desirable when someone else is paying.
Since cars to begin with are usually quite expensive in Argentina, and hold their value well, and since credit is fiendishly expensive, the idea of borrowing money (leasing) at extortionate rates that could change monthly just isnt very popular here.
Its vaguely possible that a handful of large multinationals with offices in BsAs could have some sort of special deal with somebody like Dietrich to do a few leases- but you can bet they are complicated, expensive, and require lawyers.