Here are some items you can use to raise Spec. Def.:
Zinc (using them outside of battle will raise the stat)
X Spec. Def. (used in battle and will only last for the until the end of battle/ when the Pokemon is swapped)
Power Band (Raises Spec. Def. EV's after gaining experience)
Defeating wild Drowzee's will grant Spec. Def. EV's when defeated. (found on route 2 in US/UM)
Hope I help!
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