If a shop sold lighting fixtures, listings could describe dimensions, materials and compatible bulbs. Visitors would select references to view and request an appointment. Staff would check which models are on display and which are available only by order. Confirmation would distinguish those situations so a customer does not travel expecting to inspect a product absent from the showroom.
An illustrative example to adapt to your business. It does not represent a completed project in this municipality.
Should supplier stock appear as shop stock?
Those forms of availability should remain distinct. An orderable item is not necessarily available to view or take home immediately; the listing can explain that timing requires confirmation.
How could fixture sizes be compared?
A dimension table and consistently scaled photographs would help. The site could ask for room measurements to prepare the discussion, while leaving the final selection to the customer and staff.