I found a potty on the go.
I have not experienced the boy thing yet since mine is only 8 months but I do have a 3 year old girl.
I found the greatest thing ever. It is a toilet seat that folds up into about 1 inch height and it uses plastic bags.
About a 8 months ago, my daughter and I were going to New Orleans to go to some parades with family members. I was not sure what we were going to do b/c she had just completed her first week at school in big girl panties and I knew there were no potties on the parade route.
I did research and came across this potty.
http://www.amazon.com/Kalencom-2-in-1-Potette-Plus-Blue/d...
I take it everywhere. It folds up so small that I can take it in my purse, put it under the stroller, plus I keep it under the car seat for trips. It is the best potty on the go. On long trips, when she needs to go, I put it in the front seat and she seats in it. No more public restrooms.
When she is done going to the potty, you take off the plastic bag, tie it up and throw it away.