Collecting additional information for customer profiles

I have a client who sells IV infusion services on her SQSP website. We've recently added a new password-protected page where she sells the supplies wholesale to med spas. She needs to collect certain information from these med spas before they can purchase, such as the name of the medical director, medical license, etc. We currently have a form that pops up when these wholesale clients add a product to their cart, but the form pops up for every item, and we'd prefer that they only have to fill this information out once.

I'm curious about the best workaround for this. I don't want to ask these questions at checkout because I don't want them to be viewed by the B2C customers who are purchasing regular IV infusions on the other part of the website. But it's annoying for the form to pop up every time a B2B customer adds an item to their cart. Is there a way to collect more information about a customer and have it saved in their customer profile?