When can I go topless? 9 weeks post breast reduction.

Thank you for the question.
At 9 weeks you should be healed and thus could go topless - enjoy your new breasts.
I would however advise that you apply a broad spectrum SPF50 sun block to your scars every time they are exposed to the sunlight for the first 2 years after surgery as they are more sensitive to the UV radiation and can darken (hyper pigment).
Wishing you well.
Marcus

It is rare for PS's to insist on garments and support bras at this stage but best to run this past your PS. Generally there would be no concerns but only your PS can truly advise.