Well damn you Chile for being the only country that uses this system!!! Getting it refilled in Argentina is practically impossible. We tried. We were directed by a gas appliance shop to Ocana Gas in Salta (Mendoza 1250) - a gas adaptor shop.
They sold us a small adaptor for 7 pesos that screwed on to our regulator, supposedly enabling it to be refilled. So we headed to Extingnort (Pellegrini 560) for refilling.
But it turns out it can't be done through the regulator, so we were going to have to buy an Argentinian cylinder and therefore an Argentinian regulator.
We headed back to Ocana Gas for the regulator. One of the guys patiently came and inspected our setup - the van is originally from Germany so it has a European gas fitting. We already had a hose that allowed a Chilean regulator to be connected, so they made another one that allowed an Argentinian regulator to be connected. (Custom made fitting and regulator was 110 pesos).
Then we had to buy a gas cylinder - we have a 5kg one that fits neatly into the space we have for gas cylinders. In Argentina they sell two sizes: 8kg and 3kg. But the 8kg one is too fat for our van, so we had to get a 3kg one (known as a microgarrafa).
It was so hard finding a gas cylinder shop! Why doesn't the place that refills them sell them as well?!
In the end we were directed by another branch of Ocana Gas to Gay Gas (north west corner of Av San Martin where it intersects Izaingu). An empty microgarrafa cost 290 pesos. Then we still had to go back to Extingnort to get it filled for 45 pesos! But at last we have more gas.
We haven't been cooking very much on the van's gas hob, or heating water. We really just need it to keep the fridge cold. The last few days we've been at a campsite in Salta (Xamena on Av Libano, 8 pesos pp & 31 pesos for the van per night), where there's been electricity, so the fridge has been running off that in the meantime.