With a potty-training child, you look for anything to make it easier. A few friends of mine had various folding toilet seats that you could put in the package and put in your purse/diaper bag.
I thought "what the heck?" and I bought one. It is plain white with blue flexible parts to fold for storage. We paid $10 for it from Babies 'r' us. I brought it to the mall with me probably two days later to try it out while we were out of the house.
My son says he has to go potty, so I put the seat on. But guess what? The flexible parts aren't so flexible, and as soon as I put the seat over the adult toilet seat, it folded up and fell into the toilet (luckily it was a clean toilet). I put it back in the package, and held him over the toilet seat to pee. He has since learned to deal with that, and we no longer feel the need to try this toilet seat.
If you choose to get a toilet seat to travel with, do not bother with this one. I wish I had the name of it, but we lock the packaging. It was one of those main brands, like "safety first" or something like that, btu I cannot remember exactly.
On a scale of 1-5, I give this seat a 2. Great concept, poor execution. There are ones with Disney princesses and Elmo I think that were a different brand and like a dollar cheaper. They didn't have those in stock when I bought my seat, but I have only heard good things about them.