Namecheap offers an $8 and $10 certificate at https://www.namecheap.com/ssl-certificates.aspx?aff=29535

(I included my affiliate link above, recently signed up to the program and figured why not, let me know if it is against any rules and I'll remove it.)

There is also a free cert authority but I've never used them. You have to put a link to their site somewhere on your site though.

https://cert.startcom.org/