This Dibs payment gateway for Joomla Showroom Registration Pro (Joomla 1.5 version) uses the NVP method for transmission of information. The user is sent to the Dibs website for secure processing of the transaction and then returned to your site. This means that you don't have the extra cost and management of the SSL certificate.
Osdcs.com can develop just about any payment gateway, so if you can't find it, just ask.