| Ssyvan |
If you're keen on halflings, you can pick up Cautious Fighter and Blundering Defense. Sure it doesn't use aid another, but it gives half of your fighting defensive bonus to adjacent allies.
If you pick up Madu and the Shielded Fighter archetype you can start increasing that bonus rather high. (You can also increase it by attaining 3 ranks in Acrobatics and snagging the Crane Style feat).
I know its not aid another, but it does mechanically the sameish thing.