Yeah, definitely, ebay is the way to go.
Casting your own resin bases is a bit of a pain. It's bad enough with beveled bases to get them smooth (you can sand them down), but it's really hard to work out imperfections on lipped ones. Like JamesY said, the plastic one son ebay are like, less than a quarter each.
If you want your bases to be heavier, glue a small coin under it

I used to do this for all my tip-prone metal miniatures.