So weird this got bumped now because about a week or two ago I went to Fogo de Chao and they had these on their salad bar. Loved them so much I had to google them, and one of the resulting links was this thread. . I think they were pickled or something. They're on Amazon and probably in stores but I can't vouch for the taste being the same.
There's a much loved brand of pickled pepper here called Roquito. It took a lot of research to find out what they were but my sources say that they are Biquinho/Chupetinho/Sweetydrops, all three being the same breed.
The problem I'm having is that the Biquinho pepper that SeaDuds linked above has reviews for those seeds. Some are saying they're very hot. The ones I had that tasted pickled weren't very hot at all. Not sure they were even "mild". They just had a bit of a kick to them, but nothing that would make you think "that's hot". I'd grow them, but I'm not sure I want "another hot pepper". Maybe next year I'll give them a try to see what I get.