Musick International has such a product:

http://www.musick-int.com/product/NationalAcctChange.pdf

Compatibility to Sage 300 2020 is currently in development.

Contact Sales @ Musick-int.com 

Depending on the requirement, you might consider a manual or import driven change to current customer records.

The current AR versions  allow this (didn't used to)

This will only effect national account record going forwards.