He is a very very rare drop. You can go on 50 Adventures and not get him, or you can be lucky and get him on your first try.
I've been on 3 Baron's Stocking Adventures too and no Elf Gnome or Tiny Gnome Boots alas..
I don't know if it's really of influence or just random unrelated luck, but for me the drops from the Troll Camp have increased since I put it back in storage after collecting. (just for a minute or so before getting it back out)
Thanks for the tip Andro45!
Just crafted Mr. Claus Gnome, and he looks really cute with the tiny present in hand. 22 Hour timer.
I hope the Faerie Atrium Gnomes drop more than just the occasional Snowball (especially after the snowball event)