I have just entered the doctoral program in Arts and Design at UNAM (México), and it would help me a lot to have more sources of information to carry out my research and thesis related to Fashion Films. I would thank you a lot.
You can check www.imdb.com and select 'fashion' as a keyword to search. IMDB is arguably one of the best websites (if not the best) that have an exhaustive list of movies. All movies that are listed with that keyword should turn up (https://www.imdb.com/search/keyword/?keywords=fashion&ref_=ttkw_kw_2all ). Good luck!
May I suggest that, may be focused on a specific country. Then narrow it down to a specific genre, because believe it or not, FASHION FILMS can span several genres. Hopefully it will get you a direction. and of course you can go with specific directors and their ability to narrate a story with FASHION. Such as David Frankel or Madhur Bhandarkar etc. I really hope it helps you.
I think the excellent article by Sara Pesce about the relationship between Italian Baroque, costume design in cinema and high fashion could be helpful in your investigation, doi: 10.1386/ffc.5.1.7_1.