Hi have bought a few off ebay without problems.
I/my family bought an angelgotchi, an osu/mesu pair and a new japanese red one (tamagotchi plus?)
You have to be careful, since there are heaps of fakes, so you need to see the bandai logo on the packaging and you also have to take the risk that you may be ripped off.
Postage is also an issue, there are some on ebay at the moment, that are quite cheap, they aappear genuine, but the postage is huge because they are sent from SIngapore of hong Kong or somewhere else.
I can't believe the number of fakes around. The first tamagotchi I bought was a fake version 1.