Have you tried all the chain pharmacies like servaid, etc, they should almost always have everything. Also, try all the big pediatric hospitals and clinics (pharmacies attached to them). Try all the most expensive big name private hospitals (the pharmacies in them or attached to them).
There are two reasons if a pharma product is short. Either it wasn't selling in the small pharmacies and the company(ies) recalled product and resent stocks to where it was selling better. Or the regulatory authority is about to make a decision on application for price increase. Most likely it is the first reason. So just try the bigger/better pharmacies.
As I don't know the hospitals/clinics of Isl/RWP currently, I can't tell you where to go specifically.