Job Requisition Number

We want to track the job requisition an employee was hired from. Is there a field outside of the Recruiting group where we can store the job requisition number? We don't use PeopleSoft Recruiting but would like to store the requisition number from the other system in HCM at the employee level.

@Phil-Hoskins Thank you for taking the time and providing suggestions. I like all of them, and I agree the last option we would not do.