You can get a Potion of Insight in Kresselack's Tomb that raises you character's WIS to 18 for 6 hours. You can also get a Potion of Holy Transference that permanently raises your character's WIS by +2, but lowers their DEX by -1, in Lower Dorn's Deep (where you see Malavon in the Dome). There is also a Potion of Clear Purpose (+1 WIS, -2 CON), but I don't know where to find it, or even if it's in the game.

There are several 'transference' potions that convey a boost to one stat while reducing another. For example, to mitigate the loss to your DEX from Holy Transference, you could, if STR isn't an issue, use a Potion of Strength Transference (+1 DEX, -1 STR). Unfortunately, I don't know of any potions that permanently boost STR.

In Lower Dorn's Deep, in a chest in the room where Fleezum is found, there is a chance for the Morning Star of the Gods to drop (+3 ToHit, +1 AC, +1 Wis, Memorize 2 additional lvl 1 and 1 additional lvl2 priest spells). You will have to save the game before going into the palace though, and keep killing Fleezum and reloading till it drops (random items are set on entering a level) if you absolutely want it to drop.

There is also a Cloak of Burdened Spirits (+1 Wis, only useable by good alignment) in the game's data files, but it was part of a nerfed quest reward and is not found in the game.

There might be a way to just cheat with the console and give yourself one of these items though. There are lots of magic items in IWD that grant increases to Str. Loot the Girdle of Stromnos off of dead Flozam in Lower Dorns Deep (Str set to 19), or buy Ogi Luk's Great Robe from Orrick in Kuldahar once you give him a book on Mythal Theory (18/99 Str, +2 Con, useable by Mage only). The others are random drops though, so same deal with save/reload if you absolutely want one of them:

There's a chance that one of the Orc Shamans in 4th level Severed Hand will drop a Ring of Dwarven Bone (+1 Str, can't be worn by good alignment).

Also in lvl 3 of the Solonor Tower there is a chance for a Ring of Strength to drop (+1 Str -1 Dex).

There is a chance for a drop of a Large Shield of Strength in the Undead Tomb section of Upper Dorns Deep (+2 AC, +1 Str). But you probably won't want to have to fight this battle repeatedly to get it.

There is also a Gautlets of Elvevn Might in Lower Dorns Deep (Str set to 18/51) somewhere, can't remember where.

Hickory noted there are no permanent STR-enhancing potions. All the items you mention are not permanent effects.

There is a Potion of Life Transference that can be spawned in with the console (item code USPOT3C), but I don't think it actually shows up in the game. This gives permanent +1 STR and -1 CON.

That means IWD does stick to the rules that you can only use high level divine spells when you have high wisdom as written in the manual.
Right now I play Baldurs gate 2 and Anomen has Lv7 spells though his wis is below 18.

I generated a party for IWD1 a long time ago so I can start at once if I want to. Took me 2h to reroll, so they are so min/maxed that they will not have this problem.

The manual is wrong; BG rules are custom rules. Wisdom confers bonus spells only. Divine spells are granted automatically at each level according to a table, no matter what the WIS score is; it does not have to be 18 for level 7 spells, which are granted when the cleric reaches level 14.

Thanks, everyone!