To be fair...The provision managers are doing their best. It isn't always them dropping the ball...Their suppliers, also have their own suppliers, and so on and on. A brand of bourbon for instance might have supply issues because the cork supplier didn't get enough corks made, or the bottles, labels, bourbon itself, etc...
Don't make the provisions managers job harder by trying to give them assistance. I guarantee you they already know the bottlenecks and where the causes of the shortages are coming from.