Use Zapier along with another invoice-creation service that they sync with.
Zapier is a free service non-coders like me can use to 'push' data from one service to another online, using APIs. I'm using their "webhooks" service to grab my Post data from orders and send to the different fulfillment providers I use for different products. It's a good option if you don't want to pay a developer to make a custom script for you to receive your data, and it syncs with a lot of easy things like Google Docs, mailchimp, and all the common online accounting and biz apps.
Here's the link: http://zpr.io/Z9. [Full disclosure: I don't make any money from sharing this link, but it does add additional 'zaps' (data transfers) to my account if you sign up through it. So check it out and perhaps you'll find it useful.]