They are sometimes available in the shop in your Tamagotchi. If you don't see any now, check back in about 4-6 hours*. You may not see any for a couple of days, but eventually one will show up. You can use the time to get Gotchi points because you'll need them, since it is expensive.
[* Note: shop restock times are 3:00 PM, 7:00 PM, and 12:00 AM (midnight)]