OP, very sorry to hear it is meth. This has been a very tough addiction to treat because of the lack of effective medications.
However, a paper published last year showed promising results for meth addicts treated with two drugs, injectable naltrexone (Vivitrol) and Wellbutrin. Neither of these drugs is itself addictive.
I would search for a program or an addiction doctor using a medication assisted approach to increase the chances of success. If it is a doctor, your DS would be well advised to also be in some sort of program, whether it is outpatient rehab or very intensive attendance at NA meetings.
I have helped a family member with addiction (not meth) and am sorry to say most rehabs are very disappointing, to put it as charitably as I can. They are really no accountability standards, and those are fended off by the defense that relapse is part of recovery. A bit of truth to that, but it also used way too often for abysmal success rates.
That said, the one rehab I have heard only good things about is Father Martin's Ashley in Maryland (now known simply as Ashley), and they may offer a medication approach to Meth. My family member left two rehabs after one week but ultimately had excellent success by religiously and intensively attending NA meetings.
Paper:
https://www.nejm.org/doi/full/10.1056/NEJMoa2020214