minecraft-assets/assets/minecraft/models/block/piston_head_short_sticky.json

{
  "parent": "minecraft:block/template_piston_head_short",
  "textures": {
    "platform": "minecraft:block/piston_top_sticky",
    "side": "minecraft:block/piston_side",
    "unsticky": "minecraft:block/piston_top"
  }
}