Rich snippets MarketPress

I'm trying to find the structured data for rich snippets so I can fix it because it's giving errors and missing info.

https://search.google.com/structured-data/testing-tool/u/0/#url=https%3A%2F%2Fwww.scentswarmers.com%2Fbuy%2Fscentsy%2Fzen-rock-2

This can be changed modifying the /wp-content/plugins/marketpress/includes/common/class-mp-product.php, but it's possible to do this without change the plugin's core files?

Also, I would like to add the "availability" and "itemcondition" properties?