I'm going to Brooklyn for a day this or next week.
Could any of you recommend some must see bakeshops
and/or supply shops to visit while I am there?

Thank

Go to Damascus bakery on Atlantic Avenue, and while you're there, stop by Sahadi, which is right next door. Both are Middle Eastern.

Oh yeah, and if you're on Atlantic Avenue, you're not far from lower Manhattan, where there are lots of restaurant supply wherehouses.