Arcane Admixture (AP) would be one way to do it for acid, cold, fire, lightning, or thunder.
Another way to do it is Arcane Implement Proficiency (AP) to wield a weaplement with the property you want on it.
If you just need the damage type, and not the keyword, then gloves of Eldritch Admixture (AV) will let you convert curse damage to acid, cold, or fire.