We would suggest 2 solutions available with our B2B Login Access Management app as below:
Option 1: Create a password code for the locked page(s) and send it to desired customer groups, this feature is available on Pro plan ($5/mon).
To understand how to set up this feature, you should go to How to create a passcode for a specific product? - BSS Commerce Wiki
Option 2: Create a login form for the locked page(s) and allow only customers with tag(s) to access the page(s).
Read more: How to create a login to access a specific product, collection, or page? - BSS Commerce Wiki
A drawback of Option 2 is when you have a significant number of customers, manually adding tag(s) will be time-consuming. In this case, we recommend integrating with our B2B/Wholesale Solution app (from $25/mon) to manage your customers’ registrations more effectively.
✓ Expand Shopify Registration form with additional fields.
✓ Create different forms to classify customers at the same time.
✓ Check all registrations on the app and approve/decline the registrations.
✓ Auto-add a tag for approved accounts so that they can login and see specific pages/prices.