I know there is no official Breslover garb, however are any of the chassidic garments (gartel, beketshe, shtreimel, etc.) mention in any of Rabbeinu or Rebbe Nosson’s writing?
Via the Breslov.org FAQ:
There is no typical Breslover dress-code, and indeed Breslover community gatherings are characterized by an enormous diversity of costume indicating the diversity of those making up the movement. Mens clothes range from traditional kaftans and shtreimels, to suits, casual shirts and slacks, blue jeans etc.
Rebbe Noson does strongly condemn against the trend which was becoming prevalent at the time to remove the “Jewish” clothing styles and begin dressing like a non-Jew. This included short jackets and shaving. However, in my opinion and according to many others with whom I have consulted, much of this was related to the growing influence of the so called Enlightenment Movement or Haskalah who were preaching for Jews to modernize and were strongly opposed to traditional Judaism. Today we find ourselves in the aftermath of this movement and most Jews simply grew up with these styles, they didn’t have to remove anything to be wearing what they are wearing. Therefore, the situation is entirely different.
It should also be noted that the clothing at the time of Rebbe Noson’s discussion was called Jewish and not necessarily “Chassidic.” If one would like to go in the ways of Jewish styles which were worn over the centuries that is certainly praiseworthy, but today one sees an entire spectrum of different styles, and in my opinion, far too much emphasis and sometimes pride is being placed on small details for those who are familiar with the Chassidic Styles of today. Breslover Chassidim certainly do not want to make fashion statements as this would be the opposite of Rebbe Nachman’s essential doctrine of simplicity.
A gartel (special belt worn for prayers) is almost universally accepted amongst all Chassidim. But again, the emphasis on different sizes or how it is woven certainly defy what the Rebbe wanted from us. It would probably be better to go without one then to wear one with feelings of pride, this may be why you see some Breslover Chassidim are not as careful about this. The same holds true for shtreimels, for those familiar; the color of the hairs, height of the shtreimel and other aspects have become part of the shtreimel buying process. Rebbe Noson himself writes how he gladly did not wear a shtreimel as it was only worn by Rebbes or big Rabanim in his time, he was very happy to wear a simple cap and focus his efforts on serving HaShem rather then what he was wearing. If he found it to be a distraction, certainly we must be weary of this as well.
If one has made Hisbodedus and feels that the correct way for him to follow is to go with a Chassidic garb, he should do such and certainly if appropriate this is praiseworthy. But he must be careful to do this because he feels it is the correct thing and not because he is somehow better then his fellow Jew – God forbid.
Rebbe Noson certainly does not mention specific styles, again the focus was on Jewish dress. If you live in a certain place and they have a dress code, the simplest thing would be to do what they are doing, if you feel that is the correct thing to do. A typical Breslover Chassid from Meah Shearim would wear a Yerushalmi (Zebra) Kaftan, have curly peyos (Gekrasled) and a shtreimel. If he were not living in Yerushalayim, he would wear a regular Beketshe unless the community was originally from Yerushalayim and transplanted somewhere else and therefore chose to keep their original custom.