I am not able to answer your question but I have a small experience about that that I can summarize: I have seen four different psychiatrists that gave me prescriptions for different medicines relative to DPDR. One of them happily agreed to let me try naltrexone but he also didn't seem very serious about paying attention to me (it happened that he forgot my dosage, treatment, or even the diagnosis he made earlier, he might not have been a good psychiatrist in general) , another one was very critical of the previous one and would never let me try something that was not put on the market for a disease I actually have the symptoms of (in France, prescribing a medicine out of its market authorization implies the doctors personal responsibility, I believe. And I wouldn't be surprized if it is the same in most countries) (Nevertheless that psychiatrist was also horrible in his own way and I actually have no reason to trust him much more than the previous one). The two other psychiatrists I have seen for one session each only. I did not talk to them about any treatment I wanted to try, but based on their attitude towards me I think they would have been reluctant (they were basically doubting everything I said), but I can't know for sure.
So, about naltrexone, I believe that in one paper they talk about very high dosages of several hundreds of milligrams, that seem to work for DPDR but are also known to cause liver toxicity on the long run. Another paper talks about using naltrexone on patients having DPDR as a result of trauma, and they found that just a few milligrams were enough to have an effect, but higher doses (smallest dosage is 25 mg in principle) caused too much discomfort, maybe trauma-wise. I tried the just a few milligrams option (that first psychiatrist told me that he was very ok with prescribing it to me because he was used to prescribe it to alcoholics all the time and he knew it well). It had an effect that I found significant (although not strong) just about 5 minutes after taking the fraction of a pill, which short time I was really not expecting and found very striking. I didn't know that a pill could have an effect so quickly. I took it every day and it seemed to me that the effect was decreasing day after day. I have been told in a conversation here (by Mayer-Gross, I believe) that the effect I perceived was most probably a placebo effect, because from a neuroscientific point of view only very high doses should have an effect on dissociation.
So in the end I have tried only 5 mg/day or so, but I still have a lot of 25 mg pills and I will probably try it again for a few days at that dose in the near future, once I am clear of my previous treatment (that I stopped last week). If you find a psychiatrist that agrees to give you a prescription could you please post about your experience here? I would be very interested to know how it goes for you.