C. trilineatus are pretty easy to find in your LFS. Just look for the tank labeled "Julii Cory" and you are sure to be looking at a tank full of trilineatus. There is nothing special about their upkeep, or at least nothing special that I do. I just saw some recently at my LFS and they were real cheap, like 3 for 7 bucks I think.
I like my trilineatus as they come out of hiding a little more than most others, with the notable exception being pandas which can be seen all day.