How do I get the Invoices to include receipts for expenses?

So far I really like the overall usage and look and feel of books but I just did my first client invoice and was not really thrilled with the experience. My clients typically want an invoice that has a single line item for all expenses by user. So similar to what you get when you include services by user. They also want a PDF with the receipts from expenses. I like the ability to attach a receipt to the individual expense item but is there a way to get a single aggregated receipt PDF with the invoice?

Thanks - Mike