Jackson uses as many standardized instrument parts as possible, to make field-service easier. Most technicians capable of performing repair work have easy access to them, via a variety of instrument parts dealers/suppliers.
For do-it-yourselfers, we highly recommend any of the following aftermarket guitar parts dealers, as they offer the most variety and stock.
Stewmac.com
Guitarfetish.com
Wdmusicproducts.com
Please note that they cannot identify a part by the guitar model, just the style/measurement of the part you are looking for. Most service technicians in the field have standardized parts readily available from the above suppliers. If the part you are looking for is specialized and unique to Jackson Guitars, please contact consumer relations.