The most beautiful ones I have seen in Dubai are by Selma Ben Omar who is styling now a lot of the Arab celebrities and VIPsfrom the GCC
www.selmabenomar.com
www.instagram.com/selma_benomar_caftan/
There is also a boutique in Sharjah whose name I cannot recall. I will check over the next few days and get back to you but Selma is really great.
Good luck!