There isn't one. 🙁
You might see if someone would give you a page on a secure server, or use Paypal, or somesuch. Also, keep in mind that if this .org is running their own server, SSL certificates don't cost very much anymore, and you could, in theory, run it with a self-signed cert (you'd just have to explain ahead of time why the user's browser was going to be griping on the next page load.....)