Arenas Fashion have a very good reputation for creating custom made clothes according to online reviews.
Obviously, there are testimonials on their own website too, but I never 100% trust these as there is no guarantee that the website did not just create them to make people believe they are reputable.
The only thing that worries me slightly about this website is that they have spelled 'ladies' incorrectly. To me, a website that deals in clothing for both genders, should at least get a simple thing like that right.
I realise that they are based in Thailand though, so maybe I am being too critical in my above comment.
Taking into account the fact that they are based in Bangkok, please remember to think about shipping and customs charges that may be incurred if you are in a different country.
Take a look at their website and maybe get a quotation, there is no need to commit unless you are totally satisfied.