Store within a store inventory management

[Gramandgrain]

Hi, I recently opened a space within an existing retail store. Essentially a store within a store, however the customer will only have 1 transaction at checkout for my product and the existing store's product. I am trying to find a way to see my sales and inventory in realtime in my own Shopify based on in-store activity. I tried Shopify Collective, however the customer service rep let me know that that doesn't work correctly when the retailer is using a POS to make the sales. Any other solutions out there??