FreeRadius - IIS & Outlook Web Access (OWA)

Hi, Anyone know of an ISAPI filter that understands RADIUS that can be used to authenticate to FreeRadius. This would be used to authenticate access to Outlook Web Access (OWA) running under IIS. I know of one provider http://www.tcpdata.com - but they're site is currently down and all my calls & emails have gone unanswered. Thanks! Abedi