Where to buy cough medicine in India?

I'm in Adrha Predesh for another three days, and Mucinex DM or Robitussin DM is what my dr. has me take if I don't have a perscription. I'll be going home: train to Orissa, then fly. I cannot keep coughing my head off every few minutes for the 25 hrs+ of travel. I have tried other cough syrups, but they don't work for me. I have a laryngectomey....all that hard coughing in public will be miserable and embarring and tiring. Anyone know anywhere I can buy what I need, between Bapatla and Orissa, India? I am so desperate!!