Hi Partner,
Because records in lookup field are actually data inside CRM, people couldn't access them without crm account and authentication.
Below is my thought to achieve your requirement:
1. Create a custom single line text field, let's name it "Product Name".
2. Create a static table(if you have many products) or just a static optionset drop down list for limitted products.
3. Hide Product Name by default, create custom javascript to grab selected item in static table/optionset, and sync text value to real mapped field.
(Make sure the real mapped field has been populated with valid text before submission)
4. Create a flow and trigger it when record is created or when record is updated,
add List records tile by applying Product Name value as filter to query the corrensponding Product record
5. Update the newly created/updated contact's real Product lookup field by retrieved id value from previous step.
Please let me know whether it could meet your requirement.
Regards,
Clofly
