Sorry, I don't think they sell Tamagotchis in store anymore. Well that's until the Tamagotchi Friends will come out (hopefully Bandai won't cancel them) But Ebay is your best bet on Tamagotchis and make sure to check the seller ratings and reviews before buying. Amazon is sketchy with Tamagotchis because they don't show the real pictures of the item; they only show stock pictures. If you buy off Amazon, there is a potential risk of getting scammed.
That's my input of where you can buy Tamagotchis. Hope I helped!