There are only a few items that give you mana drain resistance.
Helmets :
Porcelain Mask
(Arm:1, protection mana drain +10%)
You can obtain one every 5 days when the First Dragon Quest is active
Witch Hat
(Arm:3, protection mana drain +5%)
Dropped from : Essence of Malice
Witch 
Legs :
Depth Ocrea
(Arm:8, protection mana drain +15%)
Dropped from : Tanjis 
Amulets :
Bronze Amulet
(protection mana drain +20%)
Dropped From : Dworc Venomsniper
Minotaur
Minotaur Cult Follower
Vampire
Light Sources :
Gleaming Starlight Vial
(protection mana drain +5%)
Reward from the Threatened Dreams Quest.
Source : TibiaFandom