Flat-D Pads ($30) are activated charcoal cloth pads that you tape to the business section of your tighty-whiteys. The nice people at Colonial Medical Assisted Devices say:
This pad is to be worn inside of your underwear. Can be used daily or as needed. Can be used with panty’s, briefs and panty hose. Will not be affective with boxer type underwear. Do not use your toilet for disposal. For external use only. End your fear and embarrassment when in public.
You’ll still have to cough loudly at the appropriate moment.