There was a weapon reward in the first 3.0 adventure that gave a +4 bonus to a Sunder check.
Shatterspike
Wielders without the Improved Sunder feat use Shatterspike as a +1 longsword only; wielders with the Improved Sunder feat add a +4 bonus (including the sword’s +1 enhancement bonus) to the opposed roll when attempting to strike a foe’s weapon. If successful, Shatterspike deals 1d8+4 points of damage plus the wielder’s Strength modifier to the target weapon (the target weapon’s hardness must still be overcome with each hit). Shatterspike can damage weapons with an enhancement bonus of +4 or lower.
Strong evocation; CL 13th; Str 13, Craft Arms and Armor, Power Attack, Improved Sunder, shatter; Price 4,315 gp; Cost 2,315 gp + 160 XP; Weight 4 lb.
Might not be what you're looking for, though, now that I re-read the OP...