third-party comparable products data per product

Hi,

An administrator, having logged into the system, should be able to define which third party products a given our say XXXproduct corresponds to.
What we need here is the ability to define a relationship between two products: Our one XXXproduct, and a third party one. We need to identify which of Our product, probably by placing this data in the product node, as well as the third party company's name (either from a drop down list--possibly a node reference, or a string, which I prefer less) and a model number (can be free form).

Can any one help me how to acheive this ?
Thanks in advance!