We just use his nursery bag or if we are going out for the day we have a bigger back pack for him. X
We still use the same grey amazon backpack. It's been great, lots of room and compartments. Now it's getting to the point of potty training where we will need more outfits if we go out because of accidents and its spacious
We use a personalised back pack from my first years. It’s got a compartment for a lunch box at the bottom, space for a drink at the side and the top for spare clothes etc