Class features named “grace”
4th-level duelist (Dungeon Master’s Guide), ECL 10th. Tiny bonus to Reflex saves when unarmored and not using a shield; barely worth remembering you get. Definitely not worth going unarmored, but that’s the duelist for you.
5th-level Jordain vizier (Shining South), ECL 10th. Absolutely unlike the duelist and swashbuckler feature—more similar to the paladin’s divine grace, adding Cha to saves, but only against spells, spell-like abilities, and supernatural abilities.
Class features named “grace +1”
- 2nd-level swashbuckler (Complete Warrior), ECL 2nd. Half the duelist’s bonus to Reflex saves, but allows light armor and shields, and will grow (extremely slowly) over the course of the swashbuckler’s career. Still garbage, particularly since the swashbuckler already has good Reflex saves and should have a high Dexterity bonus, so it’s a small bonus on top of something they already have a large bonus to.
Conclusion
That appears to be it, though it’s conceivable that there’s an alternate class feature that wouldn’t have come up in my source. Nothing you can get for the swashbuckler’s grace is worth the hassle of getting grace anywhere else, though honestly Daring Outlaw is still kind of meh and I’m not sure it’s worth much hassle to begin with.
Furthermore, since Daring Outlaw actually says “grace +1,” really duelist is questionable and Jordain vizier is quite dubious.
I think most reasonable DMs would probably OK the duelist. After all, it is the same kind of bonus to the same kind of thing. But you might find Daring Outlaw inheriting the unarmored-and-not-using-a-shield restriction that the duelist’s grace has (though I recommend against this: the swashbuckler’s grace has an armor restriction, too, and Daring Outlaw makes no reference to it).
The Jordain vizier, on the other hand, has a totally different ability, and I imagine many DMs won’t allow it. I could see some DMs, however, allowing it if you had at least a +1 Charisma bonus—after all, it will provide a +1 bonus on Reflex saves the same as the swashbuckler’s, it just also does more than that.
But again, the point is kind of moot because four or five levels in some other class defeats the purpose of Daring Outlaw’s level stacking, and neither class is remotely worth it. If you were really set on getting something other than grace from swashbuckler levels, you should probably just ask if that thing can stand in for Daring Outlaw’s grace +1 requirement—I see no reason why a DM shouldn’t allow that. If they do, maybe a “reverse ACF” could be allowed, where you find a class that gets something a swashbuckler could swap grace for, and then swap that thing for grace.1
- To be clear, such a “reverse swap” is not allowed under any version of the alternate/substition/variant class/feature/etc. rules and would be a houserule you would have to ask after. DMs should consider such a reverse swap on a case-by-case basis because at least some reverse swaps may be problematic.