Public potty

I just potty trained my 2 1/2yr old she goes really well at home and walks over to her toilet whenever she has to go no problem without me even asking her.. but when we go out to the store or run errands it’s a different story, sometimes I put her in a pull-up and she waits all the way until we get home to go pee ( I try at the stores as well to get her to go potty But she doesn’t)

How did y’all do the transfer on at home potty versus public potty basically?? We have a attachable toddler potty seat that suctions to the toilet to help make it her size but what else can I do to ease her into going when we’re running errands?