You don't need any safety needle. OSHA requires that you evaluate safety needles that are available, not that you adopt their use. I don't know of any safety needle that comes in a 32 gauge.
There are many different types of needles and injections that can be used. However, most experience injectors use a 30 or 32 gauge needle or tuberculin syringe. If the physician doesn't know which needle to use then I suggest you seek a board certified dermatologist with experience in Botox for injections.
The best safety device for Botox is a very experienced plastic surgeon or dermatologist. As far as the needle goes, I prefer a 32gauge needle.
I do not think you would need to use a safety device needle for Botox to be OSHA compliant. Most people use a 30 gauge 1/2 inch needle or a tuberculin syringe. If your physician isn't sure about that or comfortable injecting Botox, I think they may want to reconsider what they are offering patients.