You can order a WMP with a purchase order. Just go to lamps.hcinfo.com, click on "Purchase" at the top, and select LAMPS WMP + Training. In the checkout page, select "invoice" for the payment method. There is a field into which you can enter a purchase order number for your own records.
After you submit the order, you will see an invoice that you can download. You will also get it by email but we suggest you download it right then because the email might go to your spam folder.