[Phantasm]

Nereidalbel is correct; Imbuement skills already DX-based skills.

However, if your GM has decreed that Imbuements are IQ-based (either because of insufficient understanding of them or because it makes more sense to him; I can see the logic of the latter), there is also an Attribute Substitution Perk in Power-Ups 2: Perks, which admittedly has to be bought once per skill. Fortunately for skills which require specialization (like Imbuements), it covers all specializations of the skill.