How can I get a Galactic potion or elixir? Don't see any in the shops..

You actually make a pet galactic by visiting the Coda Caves (https://subeta.net/explore/codacaves.php) and doing a quest for Iltallo (https://subeta.net/explore/caves_quest.php). He will ask you for one of every color of coda caves crystal. On the 6th and 7th of every month you can mine these from the Coda Caves, but you can also buy them any time from other user shops for pretty cheap. Once you submit all the crystals, Iltallo will change your selected pet into galactic.

Thank you :)