Ayling wrote: .... how do I define who these people are, and only show the product to them?
Both previous answers to your original question are pointing into the same direction: using Joomla's ACL and HikaShop Business' restrictions.
1. Get HikaShop Business Edition (sorry, no other one has the required feature).
2. Create a new Joomla usergroup with "Registered" as parent, name it e.g. "Specific Company".
3. Add customers of that specific company to the new usergroup.
4. Create a new Joomla access level, check "Specific Company" and "Super Users" only (eventually also admins?).
5. In that special "one piece of clothing" product, use the ACL as shown in the link to make it accessible for "Specific Company" and admins only.
6. - 999. Enjoy all the other advanced features of the Business Edition.