you can by a world insurance through e.g. Home
, or write Nowag in germany firstname.lastname@example.org
Although not all countries are covered, Colombia for example is not and you will have to buy insurance at the border, which is another option for the other countries too altough sometimes it is not available at the border itself and you have to drive to the nearest bigger town.
We travelled through all SA countries again last year and this time have been asked quite a few times for insuranceproof in the Guayanas, Venezuela, Peru, Paraguay and Argentina.