There is a private clinic in Glasgow called Clinic 158. Not only will they prescribe you naltrexone, if medically suitable, but they will also prescribe as per TSM. It is where I first got my tablets from in October 2013.
Cost-wise you are looking at around £100-£150 ish for the consultation and the first 28 tablets. That was the price from a few months back when someone else went to them.
If you don't drink every day, then 28 tablets will last a while depending on how long you do drink.
Very Important:
Please be sure to keep a drink diary, logging how much you drink over the coming couple of weeks and how much you drink when you get the naltrexone. This is VITAL not just because it is a suggested thing to do with TSM, but also because you will need it when you get back home and get to see alcohol services. For two reasons. Firstly, they will only ask you to complete one at your first appointment anyway. But secondly, the NHS usually only prescribes naltrexone to those who are already abstinent and to help with their cravings. In your case, you will be able to show them that this method is working for you and so it will be extremely difficult for them to decline to prescribe you when you have documented evidence that this is working for you. For info, naltrexone costs the NHS less than £30 for 28 tablets so your request is hardly going to break the NHS bank

If you need any further information, you can find me at
http://www.cthreeeurope.com which is the European 'arm' of Claudia's C Three Foundation, and I am based in England so know the NHS systems very well. I rarely post on this forum so emailing me via the website is always the quickest way to get me.
Naltrexone can be ordered from abroad BUT it takes about 2-3 weeks for delivery anyway, in which case you will be in Scotland. Plus, if possible, it is really useful to have a physician assess you to check that naltrexone is medically suitable.
Not sure where you live now, but if you are not going to be in the Glasgow area of Scotland in 2 weeks, then Clinic 158 will often do a telephone consultation and are often willing to prescribe if there is nothing in your medical history that indicates to them that they must see you.
The telephone number to talk to them is 0141 357 7357.