According to data compiled in this reporting, it does not look like second generation evolutions that require an evolutionary item are available in the wild.
Gen2s that require items in evolution are not available in wild, this incluidng those from Gen1 including Porygon2, Bellossom, Slowking, Steelix, Kingdra, Scizor, Politoed, as well as Sunflora from Gen2. Despite people have shown screenshot, I have not read evidence that these were caught in wild (unless there is a bug in multiple trackers). Blissey and Crobat are availabe in wild, because their evolutions do not require stone. We have not seen Umbreon and Espeon in wild in San Diego. We have data for 10523 rare spawns and these were not observed. So I can say for sure this is the case!
This thread has amassed data over a 24 hour period in Lisbon, Portugal and recorded 0 item evolution spawns, which supports that they are not available in the wild.
To start with something we are almost certain of, there are no spawns of Heracross or Corsola. Also no Porygon 2, Espeon, Umbreon or any other Pokemon that uses item to evolve have not been found, which helps proves that they dont spawn in wild.
Another thread that has compiled data that was taken over roughly a week says that exactly 0 Porygon2, Sunflora, Steelix, Scizor, Slowking, Kingdra, Politoed, Bellossom, Umbreon, or Espeon have spawned in that timeframe.
Zero spawns of evolutions that need special items or special circumstances (espeon/umbreon).
Since Crobat and Blissey do not require evolutionary items to evolve, however, these appear to be catchable.
It does not seem like Umbreon or Espeon have been seen in the wild, though. This may be due to the friendship requirement to evolve them (aside from the one-time naming trick).