I have a lot of success with etsy, you can look around quite a bit and there seems to be seller somewhere on the site for EVERYTHING, most of the time people have the $35 free shipping thing going so if they're a good shop you can get a lot without paying a ton. Etsy support is really good at getting you your money back if its the wrong plant/dead on arrival etc.
Small shops like to trade and stuff too, unless you have a reason to limit to ebay I'd try there