Yes, there are companies that offer GSS API v2 SAP certified third party products 'just for Kerberos'. You can find details by searching on SAP Store (http://store.sap.com).
Also, I need to let you now that due to rules of SCN, discussion about third party products is not allowed on SCN, so posts might get deleted if details are discussed. I will discuss with you outside of SCN instead.
Thanks
Tim