All of these Pokemon are smaller and cuter than Mt. Mortar, which should be good enough for you.
Dragonite: evolve a Dratini from the Dragon's Den, Safari Zone, or Goldenrod Game Corner
Smeargle: Ruins of Alph or Safari Zone
Lugia: Whirl Islands
Pelipper: evolve a Wingull from Vermillion City
Latias: roaming Kanto (HG only)
Latios: roaming Kanto (SS only)
Mew, Rayquaza, and Arceus are unobtainable without trading.
I'm too lazy to list all my sources, but I can link you to any specific source if you want.