Check out below my question on Supplier Sourcing Strategy?

I trumbled a bit to understand the issue , a good answer would be : do you have your sole supplier BCP plan ? do you have the right to audit the supplier to confirm it is working ? 

Assuming you have no other option then a good contract combined with a good insurance policy will do the trick.

 

interested in other views as well

It really depends upon what is being supplied. If it is a raw product, then the storage location could be duplicated within the same geography. As there is a monopoly, I would have to ensure that the source has adequate resilience in place and has considered the high impact/low probability threats.

Some major factors moving companies toward using fewer suppliers are investigated along with the advantages and characteristics of a good buyer-supplier relationship and the problems with long-term relationships.company can be highly involved with only a limited number of suppliers and needs a variety of relationships—each providing its different benefits

I am more going to Mark  point of view it depends on what is being supplied.Iin addition we must conduct a Vendor assessment and have an SLA with the vendor and increasing the stock .

 

It may sound a bit crazy, but best thing from my own point of view is to go with the say "keep your enemies close to you. meaning sign a sharing contract ( get them to buy some shares) with those suppliers as they will benefit from your gain and will lose with your loss. This will reduce the likelihood of you not being provided with your supplies plus might decrease the monopoly pressures.