Zapier Integration - doesn't get Opportunity Custom Fields

I’ve set up a Zap triggered when an Opportunity moves stage - it retrieves the Opportunity info and adds it to a Google Sheet. Simple, does the basics of what I need.
However, it doesn’t retrieve the custom fields, or Products/Subscriptions info.

I set up a 2nd step to then “Find Contact” so I can pull in more info and all the custom Contact fields, but there’s no similar option to “Find Opportunity”

I understand that Webhooks might be a solution to getting all the Opportunity custom fields, but that’s above my knowledge and skills at the moment.

Is there something built-in to Zapier or Keap that I’m missing, or is there an easy to follow guide on using/setting up webhooks for Zapier/Keap? I wouldn’t know where to start.

Any help would be appreciated!