There’s a set I’ve had my eye on, on Amazon that is a LEGO train station. Part of the set includes a truck with a trailer that has a portable-potty. And one review includes a picture of the inside and claims it has a piece of poop inside the toilet. This is the Amazon listing here https://a.co/d/2QcJbns
then you're going to have to get the police station modular, because the jail cell toilet has pee and poo pieces in it. and the Ninjago city markets also has the first working Lego toilet.
sorry if my knowledge drop costs you an extra $600.