I think if you found anyone with experience with Asperger's alone would be enough. Borderline Personality Disorder is commonly associated with dissociation, and pretty much every mental health worker, psychiatrist, social worker, and psychologist I've ever met was quite familiar with the condition as well as dissociation, though only a small handful have the understanding of the specific challenges Asperger's bring with the diagnosis. I can't see dissociation being treated much differently than it is for BPD.