How about Phaant's luckstone, from Ghostwalk, page 72? It costs 1,000 gp, only has to be in your possession to work, and lets you reroll any roll you've just made. It's a single use item, but it seems like a good last line of defense, after an amulet of fortune prevailing, luckblade, or mantle of second chances.
I second pfooti on amulet of fortune prevailing and dt on robe of the vagabond (which does not take up the robe slot, despite the name).
Also, the most recent printing of cats-eye brooch is in Magic Item Compendium.