When travelling around London, I usually follow the standing advice and use an Oyster pay-as-you-go card for my tube/bus/train/dlr journeys. It works well, as I can load some cash on every so often, quickly breeze through turnstiles / onto buses, and I know that after a few journeys in a day my costs will be capped and all subsequent journeys will be effectively "free".
Historically, when in Paris, I've tended to just buy a carnet of 10 metro/bus tickets, often from the shop on-board the Eurostar on the way. However, I've noticed recently that almost everyone else is using Navigo cards for their travel, rather than the paper metro tickets. Is it possible to get an equivalent to an Oyster pay-as-you-go for Paris as an occasional tourist? (Let's say 2-5 journeys in a typical day)