How to use public toilets correctly?

Salam I’m usually out during the day and have to use public toilets when I need to go. Most of the time however the toilets are dirty and I feel unclean after using them. Sometimes have to stand up which I know is wrong but the toilets are dirty people do their business all over the seat sometimes. What to do in this case? I know this will affect my salah it probably isn’t even valid but what’s the alternative if I have to rely on public toilets during the day ? Of course I can use the mosque toilets when I’m there but I mean in general when you’re out and have to rely on public toilets. I can’t shower before each salah because I’m out and I can’t take a change of clothes with me every time Please help