I've found a good way to get at least a little cleanliness in a public toilet. I carry a supply of Purell wipes with me in my car, and slip one into my pocket if I have to use a public restroom. I wipe the toilet seat, wait maybe 10 seconds, then dry it with some toilet paper before I sit down. Of course, if I'm in a flare this process is considerably shorter and I'm focused on trying to sit down ASAP.