I have a Red Butterflies shell. I found it at my local Walmart (in NC). I paid the standard $14.99 - wouldn't bother paying any more on eBay since it was only a matter of time until they came in stock.
I'm hoping to find a Green Peacock shell as it is my favorite (butterflies being second). I don't own any other infra-red capable Tamagotchi so it will be nice to have a second.