I recently found my seal leaking while in a remote location on a hunting trip. Not having any suitable lubricant on hand (gun oil didn't work, BTW), and the smell getting worse from not having that liquid barrier I resorted to filling the bottom 2" of the bowl with liquid fabric softener that I had with me.
I left it overnight and flushed it in the morning. The bowl has been holding water since! I'm not sure exactly why it worked, but it did. The bowl hasn't held water this well in a long time.
It did bother me though, that the seal is only a year old.