How can I set up a way to limit what products customers can purchase (or even see)?

I sell to over 50 customers consistently. I have 6 brands internally that I sell to these customers and each brand has the products segmented into Finished Goods or Service Parts. I have different contracts with each customer that limit which combinations of products they can purchase. So some customers will be able to purchase both Finished Goods and Service Parts from certain brands while only being able to purchase one or the other from another brand. This will vary for every customer. I was initially looking for solution within Customer Data Management by using Classifications then create Product Catalogs