If you´re feeling paranoid or run into a jam you can contact the guy below for some Argentine liability insurance.
ROBERTO JORGE ARTURI
-Asesor de Seguros-
Adr: Hualfin 1032, 6 piso B (1424), Cap. Fed.
Tel: (+541) 4328-9109
and there´s more:
-he´s a freelance insurance agent, a real pirate, knows his way around, he can get you any insurance you want. I think he would even insure the Titanic. As I said previously, you don´t want to find out who the hell is gonna pay for damage, but what is a fact is that you will get nice, good looking insurance papers which are valid. Cost should be no more than aprox. 20 USD a month. Minimum coverage is 6 months, but you pay per month. My advice is to just pay once so you get all the papers and then don´t pay anymore. (Well, I guess I´m a pirate as well.)
Liability insurance in Argentina is called "Seguro contra terceros no transportados"
Whatever you do, make sure you have something to show the cops, even if its your foreign (not valid) insurance, preferably in a foreign language. They do stop you sometimes.