How do I create a Merchant Center feed for a local inventory (Shopify)?

Question

Online shopping

I need to create a data feed for Google Merchant Center in order to run their "Local Stock Free" program.

To do this, I need to create an additional feed in the Merchant Center with local products .

It can be downloaded by URL in XML format, automatically on a schedule. It cannot be formed from the main feed (Content API)

I have a data feed ( link

), but MC does not accept it, because it does not comply with the rules inconvenient

How else can you create this feed - simplifying the process?