if you have access to a syringe of some kind then drink plenty of water and buy some water balloons, when your nice and ready to burst make sure to pee in a glass, now using the syringe fill the water balloons to near bursting point, at least 2, the more you use the more daring is up to you, now diaper yourself and get ready to go out to the mall, wait until you get their and using the bathrooms put the balloons into your diaper, bonus points if you don't use a toilet stall,
now go shopping and hope that they don't pop, because depending on what kind of diapers you are wearing they might not be able to hold a lot of water, plus it will burst very fast and not slowly like urinating so it might overflow, and people might hear your balloons popping, also the balloons create a buldge and is very embarrassing, if you need to pee at any point go to the bathroom and to a urinal undo your pants but just pee in your diaper and hope nobody notices, have fun doing this
and report back, I don't need pictures btw