You should be able to do a calculated metric using the Approximate Count Distinct function...
Approximate Count Distinct
Product
÷
Container - Segment (UV ID Exists)
Approximate Count Distinct
Logged in UV ID
(this is assuming you are tracking an ID or GUID for your Unique Logged in Users)
The inclusion of the segment (simple Hit Level Segment where UV ID exists) ensures that you don't count all the UVs without an ID as a single user in your distinct count logic.
