I dont have sun crystals and dont know where to get them from. I only just finished hamelin so I'm not sure I can access any areas with the mobs that drop them. I don't really want to waste exp by leaving my familiars in second form.
You can find Sun Crystals (and the other forms of Crystal too by the way) up on Billy Goat's Bluff from a Harvest Point. It's located directly to the east of the Swan Islands, on the NW portion of Autumnia. It's accessible as soon as you get the ship.
You can farm Moon Crystals from the Fluorobors monsters there as well.
You can farm Planet Crystals at that point off of Lubbercub on Shipwreck Shore. --- I sometimes feel as though life is a curse that has been placed on the living. I envy the unborn at times.