Shortages happen because the production is so localized,, it's easy for rain at the wrong time of the year to ruin the Tasmanian crop and the production houses are legally bound to not stockpile more than 8 months supply.
For this reason they have started poppy farming on the mainland this year. On a vast scale.
Opiate farming and production is probably the most regulated industry on earth next to nukes, I just don't see how a company like Glaxo could get away with producing say twice as much finished product as their known raw material intake would allow for.
Mexico, China, Russia may be markets,