imo 2 good bets for everyday use are either scint scarf (exo resists) or helm of zeal (ele resists, which isn't nearly as valuable for wizard due EB, but it does have fear imm which can be lil more difficult to fit)
helm slot has a few options for run-specific immunities, so depending on the run you could save a ring slot by swapping on myco wb hat or abo one; or exo array for conf imm, kinda rarer hive stun imm hat for stun (not much use for stun imm tho as wizard), ely weird hat for weird imm (not much need for that in general outside abos and some abyss), lifebane crown for pwk imm (also not much need for this outside PoM bossfight, until limbo)
conf imm is prolly most common/most often "needed" imm of these, for various bossfights, so exo-array is a good item to have in general for swapping on when needed. i'd definitely consider saving ring slot with a wb helm for underwater runs, depending on rest of your gear, but scarf (or UR version of it) is prolly my best recommendation outside conf fights. exo dmg is often heavy in LL+, exo kb is an issue for mages, and unlike sorcs, who have a basically "required" helm slot (thid or azz slot mask), wizard helm spot is pretty open for swapping as needed. there is ofc a crappy lowbie slot helm for wizards but i wouldn't bother with that, use that precious gear slot to fill holes in your kit.