I am implementing ERPNext in two garments in Bangladesh.
I have an issue that after starting a production one or two raw material some time gone out of market, that time we buy a new raw material with same ingredient. Price and other stuff will be same just the item will change.
You can quickly create new BOM for an Item by duplicating existing one. Replace items based on the availability. Create Production Order for the New BOM.
Option 2:
Manufacturing Setting > Backflush based on Material Transferred
This option will allow you to use existing bom, but transfer new Items instead of one in the BOM, and complete Item production.