There's only one set of Gauntlets of Dexterity.
The following is a (probably) complete list of strength-boosting items:

Mauler’s Arm: Increase bearer’s strength by +3, max 18, when wielded (original: Set to 18)
Gauntlets of Ogre Power: Increase wearer’s strength by +4, max 19 (Original: Set to 18/00)
Girdle of Hill Giant Strength: Increase by +4, max 1 above character’s max (was 19)
Girdle of Stone Giant Strength: Increase by +6, max 3 above character’s max (was 21)
Girdle of Frost Giant Strength: Increase by +7, max 4 above character’s max (was 22)
Girdle of Fire Giant Strength: Increase by +8, max 5 above character’s max (was 23)
Crom Faeyr: Sets strength to 28. (was 25, absolute max)
Angurvadal: Increase strength by +4, max 4 above character’s max (was 22)

Two of them are available for purchase pretty early on... The ranger in particular can bump his strength up easily.

With Fire Giant Belt and +1 str from the Machine of Lum the Mad, a 20th level barbarian could hit Str 30.... but not in this party.

I will need to come up with a bit more for Viconia to do since we have a cleric of Shar in the party. I figure they'll probably try to find her someplace to stay, but I'm not sure where yet. I think I'll just go with whatever they come up with. Copper Coronet or Ribald Barterman are likely to be good choices.