I have ordered from ebay and had good results. Just read their cautions and disclaimers - the more, the better, as it means they care and try to have their live cargo arrive that way. Most say they only ship Mon-Tues, as shipping later in the week could get the package hung up over the weekend.
Pick a seller as close to you as possible (click on their name and there should be some info about where generally they're located) so the distance won't take too long and the fish won't be as stressed. This is especially important in the middle of summer or winter; they pack accordingly but time is of the essence.
Sometimes they throw in freebies, an extra youngster of the same type you ordered. This has happened to me a few times; I didn't necessarily want someone extra but when it turned out that the original fellow I ordered died a few days later (the only time that ever happened), well, there I was with his replacement already. This freebie guy is still doing fine a year later.