Hello,
With Multifeeds for Google Shopping, you can create daily updated XML feeds that include your product. The app also hosts the generated files and you will be able to use the feed URLs for the product comparing services. The XML files can be fully customized, including the tags and the data that needs to be included. It can also be scheduled to be refreshed at specific times of day or to run more frequently than once a day.
I went through the comparing service documentation and it only require the feed to be “hosted on the Internet”, but you mentioned it needs to be hosted “on your store”. Did you mean it has to be on your store domain, as it seems not required by the comparing service?
Disclaimer: I am the developer of the app. Happy to discuss any issue you may have with our app or any other solution that you are using.