I would like to create juju zombies by using an item. Are there any stock magic items that can do this, for example by allowing the user to create undead as the spell Create Undead? I can't create a custom magic item that simply performs a Create Undead because my GM doesn't allow that.
Any creature slain by Ungarato—either as the effect of a critical hit or otherwise—reanimates as a juju zombie (see Bestiary 2) 1d4 rounds later under the control of the sword wielder. The sword can control up to 32 HD worth of juju zombies in this way. If this amount is exceeded, undead are released from control as per animate dead.
So, its neither a stock item, nor readily available. But i had to mention it.
Creating juju zombies
The spell create undead when employed by a level 11 caster can create juju zombies. Hence, a staff or a scroll of that spell is the easiest magic item that allows juju zombie creation.
Other than that, the onyx spear (né the Wendifisa spear from Inner Sea Combat) animates the wielder as a juju zombie if the spear's linked onyx is within 100 ft. of the wielder upon the wielder's death. A creature that distributes such spears to his future juju zombies must have his own way of commanding the resultant juju zombies as they are free-willed upon their animation.