Ebay is 50 50 at best.......generally people don't know how to package palnts so they make it.
Buying plants online it best to find the source close to home.... Not sure where you live so I hard for me to tell you were to go.... Remeber to look at shipping cost because they are going to charge you the same for one plant as they would if you order 100 plants.
If you in the SE try Floridadriftwood.com
West Coast arazonia aqutics a good choice, aquariumplants.com even better
NE Petsolutions.com and Foster and Smith offer alot of standard plant and a few exotics.
All sell plants and know how to ship them.... never let a plant stay in the dark for more than 2 days they will melt. never order plant in the dead of winter witout paying for a heat pack. never order plants when you can have someone home to receave them, you don't want them sitting on your porch,
I order plants and livestock all the time online it the only way to get the plants I like....
If you have a good LFS in the area see if they can order them for you. Check the chain stores they sometimes have a few nice plants.