Procurement from alternate plant and external vendor simultaneously

Dear Experts,

I have a requirement as below:
I have a SFG material which is externally procured(from China) in plant A and in-house manufactured in plant B(made in USA). There are few clients who send order in Plant A and ask for the USA made SFG part to be used in FG assembly for better quality (STO process). Else by default it is procured from China. How do I replicate this scenario in MRP?