more on server certificates

Hi Has anybody got a digital certificate (with the extended key usage attributes required for PEAP) installed on their FreeRADIUS box that has been signed by a commercial trusted CA? I have come to suspect that this is impossible due to the fact that Verisign are the only company marketing such a product and it can only be installed on a Windows server (as the online purchase system only works if done from the target machine using Internet Explorer and Xenroll). Thanks Ben