Answer: supplier search
Step-by-step explanation:
Portillo's Fast Food restaurants are in the supplier search stage in the business buying process. The supplier search refers to the stage of the business buying process whereby the buyer or the company seeks the best suppliers or vendors.
The company can compile a list of suppliers and make a research about them to know the one that's most appropriate to carry out the job at hand and will be most effective and efficient. This can be infered from the question as Portillo's is looking for a vendor that can provide a product according to its new specifications at a price that is less than what it was paying in the past.