There is always the PSX-AC electronic breaker, available from Charles Ro and Tony's Train Exchange among many others. This would be my choice if I had electronics in my engines.
Then there is this video about breakers for ZW's Lionel Trains ZW Transformer Overload Short Circuit Protection. This was posted before by someone else here on the forum, but I can't remember who it was? I thought it was interesting and it should apply to other transformers or power supplies as well.
There is also the Lionel PH-180 power supply that has an excellent breaker (and you would also get more power to the track). Also available at Charles Ro and many other forum sponsors.
Along with GRJ above, I've also always been a little leery of those inexpensive breakers that can take quite some time to trip. I have never tried the method used in the video, but it seems like a better way to size the breakers to me? Maybe someone more knowledgeable will comment.
Personally, I like over kill, and have both PH-180s and PSX-ACs on my layout. Or as a good friend once told me, "anything worth doing is worth overdoing" 
