I can't recall the name of the feat offhand, but it allows a monk to use any specific light weapon as if it were a monk weapon.
The sai and jitte are found in OA.
Jitte, 5 sp, 1d4, 20/x2, 2 lb, bludgeoning
Sai, 1 gp, 1d4, 20/x2, 2 lb, bludgeoning
With the jitte, you get a +2 on all disarm checks; with the sai you get a +4 for disarming others, but not on the opposed roll. With both weapons (in the OA setting), monks can use their unarmed increased rate of attack.
Greg