Use this list (https://www.gov.uk/government/publications/endorsing-bodies-innovator-founder-and-scale-up-visas )to find out who can endorse your application for an Innovator Founder or Scale-up visa.
An organisation can only issue an endorsement if it is on this list. If you have been offered an endorsement by an organisation that is not on the list, you can report it. https://www.gov.uk/report-immigration-crime