Ebay Revise Listings

Hi Liam,
Basically I have a phone case shop on eBay with personalised designs printed onto phone cases.
I currently have 4,500 listings each with variations for which phone model the customer chooses.

I need to add new phone models to these current listings as new variations but can not figure out how to do it without doing it individually which would take an extremely long time.

I know it can be done with file exchange but I just cant figure it out.

Could you please let me know if it can be done and how much it would cost for your help.

Thanks
George