You can buy one with Bitcoin here, but you have to buy a whole hosting package from them.
https://www.anonymousspeech.com/anonymous_hosting_ssl.aspxYou can't just buy a certificate from them. Also their prices are not cheap. They charge 49.95 / month for their idea of cheap hosting and 29.95 / month for a yearly plan (it's usually more than that but they are doing a special offer this month).
https://www.anonymousspeech.com/anonymous_hosting_ssl.aspxThey also have these rules.
Limitations
Please note that our legal advantage is not a free ticket for any illegal activities on our servers. Do not apply if the content of your website contains
Child Pornography
Organized Crimes
Spam
Copyrighted Content