In the US, on store shelves, we only have terrible nappies (diapers, in the local vernacular as mentioned by another poster), suitable for light bladder leakage or small dribbles.
Fortunately we also have some of the best diapers available online, and if you’ll be here for a few weeks that shouldn’t be a problem to have them sent to you (should only take 2-3 days or so). I get all of my incontinence supplies from northshorecare.com, and I highly recommend the Supreme and MegaMax diapers.
As someone else had mentioned, if you absolutely cannot have anything shipped to you, try to find a “medical supply store” - they’re like an enhanced pharmacy that carries better goods. Some have an above average diaper stock, others do not. Only 2 or 3 in the entire US might match what you can get on NorthShore, so it’s best to order online if you can.