Hello Tim,
Method does not have a default report that displays invoices of customer's who are categorized under a specific lead source. It would have to be created through the report designer. You would have to make a report based on the invoice table (or transaction table). Then link back through the customer's to the lead source. You will have to use one of the customization services or take a look at our customization resources if you are going to tackle it yourself. There may be a report you can use as a basis to create the report from.
The report designer may look and act outdated but it is powerful. Unfortunately, you do need a pc to run the program. It is by a company called DevExpress and you can Google more information on XtraReport, which is the program's name.
Greg