Where can I buy Argentine Pesos?

Sounds practical. I’ve done that myself while travelling. Just be sure not to flash it since pickpockets are everywhere in the world, and they’ll be watching.

I’d also bring a few smaller bills ($5,$10, $20’s) for tips and if you just want some 'walking around money without converting a Benjamin.

I suspect (as others here have said) that there will be a place at the departure airport with Argentine pesos available before your flight…Argentina simply doesn’t have the quantity of flights/tourists to make it worth the effort for banks/exchanges to get into the business (IMHO).

Enjoy the trip and the Rugby.