You are speaking of Extended Validation Certificates. They are basically common X.509 SSL/TLS certificates, the only difference consist in a different (stricter) identification procedure needed to obtain them (compared to a "normal" certificate).
In order to issue a EVC, the Certification Authority requires the applying Company to provide some more documents and performs an "independent" audit on the real identity of the applicant.
The string displayed in the green bar by the majority of recent browsers is not a "custom message" but the name of the Company as verified by the CA.
Afaik, all major CAs (VerySign, Godaddy, Thawte, GeoTrust and so on) are able to issue EVC.
A technical note: an EVC is not cryptographically "more secure" of any other X.509 certificate in any way. It just provide a stronger assurance about the real identity of its owner.