Looking for a Concentraion Bonus

[gabrion]

Can anyone think of a non-custom item that gives a bonus to a character's concentraion checks? Thanks.

Edit: The one item I'm aware of right now is a psionic shard, but I'm looking for something more permenant that doesn't need activation.

 

[javcs]

Constitution bonus items.

 

[gabrion]

Constitution bonus items.

Well of course that helps, but I'm looking for an item that operates similar to something like eyes of the eagle, but giving a bonus to concentraion rather than spot. I know the rules for making such items are very simple, but I'm in a game that doesn't allow any custom items, so I need to find this item printed somewhere.

 

[boolean]

Tunic of Steady Spellcasting, Complete Adventurer. (Despite the name, the bonus applies to all concentration checks, not just spellcasting.)

Third Eye (Concentrate), Expanded Psionics Handbook.