The requirements that ISO 13485 describes with regards to supplier agreements is:
7.4.2 "Purchasing information shall include, as applicable, a written agreement that the supplier notify the organization of changes in the purchased product prior to implementation of any changes that affect the ability of the purchased product to meet specified purchase requirements."
For some further information and background, refer to ISO13485 Section 7.4 Purchasing. That is mostly the extent of the ISO/FDA medical device requirements, to my knowledge.
Beyond the ISO requirements, we want to think about what else might be critical so we can use this agreement, hopefully for a while with new suppliers. We may want to consider shifting some of the liability in the agreement; for example, if we determined that there was a bad batch of load cells that failed after 1 week of usage in the field, where would that liability fall?
We would like a Supplier Agreement that includes the above, and remains somewhat general so we can use it with all of our suppliers with only minor changes required. We have suppliers that range from label makers to load cells to steel sheets, for some more general background.
As part of our ISO 13485 Documentation toolkit, we have prepared two types of quality agreements: one for critical suppliers and a quality agreement for subcontractors. The subcontractor is a company who produces something especially for you like in your example. Critical suppliers are all those suppliers which can have a significant impact on the quality and/or safety of your product.
Preview of those two contracts you can see on the following links: