There is a setting to pick the email template in Settings > General Settings > Request further transaction actions email template

By default this is set to the email template Default Invoice Payment Request Email

On the Accounting - Tenants page, you can change the Tenant Type filter to Leads. Select a lead and create an invoice in the transaction manager. The 3-dot menu on existing invoices will then have an option for Request Further Action that will open a modal to send a payment request email to the lead.

The email will contain a link that just goes a page similar to the rental application, except it only has the payment section.