I do not have incontinence first thing I might mention. They have been times though I had wet trumps and I thought I have pooped myself.
The first thing I suggest if you have a raider key try to access the disabled toilets. The Raider key is a big key used to open disabled toilets. You should be untitled to one.
If it is America and you do not need a key then I suggest waiting for the next person to walk out of the disabled toilets.
If you can not get into the disabled toilets or you do not have a raider key try going to the baby changing toilets. If anyone questions you you can say you could not find anyone with a raider key. Or you prefer to change in the baby changing area.
If you feel too embarrassed about going to the baby change area then just do what everyone else suggested go to the toilets and change in a cubical.