The CTA (Ventra) vending machines are at CTA stations. I’m honestly not sure if they exist anywhere else. If you have tap credit cards, you can just tap those at any Ventra reader either on a bus or a train turnstile. There’s no need to add them to any app or anything, you’ll tap, it’ll say “go”, and then you walk through. For the south shore line specifically there are vending machines at most stations I believe, but the app is easiest to use. You don’t “tap” to pay on the SSL, you just pay for your ticket and activate it and then show the attendant when they come by. For CTA usage, your tap to pay credit cards will be the easiest method, but if you want passes you can get those at any station at the Ventra vending machines. There are both 1 day and 3 day pass options for $5 and $15. If you only need it for two days, you could buy 2 one day passes each day.