Cross Referencing part number or multiple part numbers

Is their an easy way to add an extra field to the database as an Other Part Number or Cross Reference Part Number?

I have noticed my competitor sells the same items I have and has created his own part numbers. Plus I have used some of my vendor’s part numbers rather than the manufacturers due to the fact I entered the product that way some time ago and now I buy the same item from multiple vendors.

Currently I have added text at the bottom of the description “Similar to XYZ Companies item # 123-456” I would rather have it as a field in the database so in the future you could print out a list of products that have multiple part numbers as a cross reference section for sales members.