I've been buying Comodo authenticode certs for years through KSoftware - http://codesigning.ksoftware.net/. The prices are much lower than buying directly through Comodo and the service is excellent.

If you're on Windows, one thing to keep in mind is to use IE or Firefox when buying the cert. After the purchase is approved, you need to navigate to the site in the same browser that you purchased it, and only IE and FF are supported.