Accounting Subledger - How do I track credit card fees associated with donations?

Donors give donations on our Website through a third-party (Funraise). Funraise syncs with Salesforce, and creates an opportunity in SF. We use another third-party (Stripe) to process payment and subtract the credit card fees. We would like to track the amount of the donation minus the credit card fees in Salesforce. Any suggestions on how to do it? We are setting up Accounting Subledger, and need the donation amount to include the credit card fees.

Thanks,

Manny