well you could contact a few different companies,
Wilton
Americolor
Ateco
BakeryCrafts
DecoPac
Magic Line
For boxes/boards/containers I would suggest Bunzl if you are planning on selling a lot.
Any manufacturers that make the items you like or would want to recommend to others. I would start by contacting them.
BakeryCrafts and DecoPac have a lot of different stuff that a bakery would use so that may be a place to start if you aren't sure what brands you want to start with. One of them carries ateco but I don't remember which one.
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