Unfortunately many clinicians still view this disorder as controversial, and will not touch it with a ten foot pole. Some won't because they don't believe in it, others won't because they haven't had training in it and feel like it's 'over their head'.
I live in a small city (70,000) and have only just now found a psychologist who can work with me and my DID after well over a decade of searching. I need to see a psychiatrist to get the diagnosis reconfirmed, and my T told me yesterday they will fly in a psych from another city to do the assessment as there is not one in my city who has enough experience with DID to do it. That's crazy, right. With an incidence of around 1% of the population it is appalling that the psychs don't have their **** together about this disorder yet.
My T has only minimal experience with DID, but she has had training around structural dissociation as she has recently trained in EMdR therapy, and here training in dissociation is a requirement of becoming an EMDR therapist. I have read that is starting to be a requirement in the US as well. So maybe that is an approach you can try... seek out an EMDR therapist and ask them if they have knowledge abut structural dissociation. My T isn't all that experienced with DID but she is very good, and she is picking things up quickly.