Hi Ravi,
During the download, you can rename the file from com.sap.portal.support.browse.default to com.sap.portal.navigation.afp.masthead.zip or com.sap.portal.navigation.masthead.zip and select the file type (save as option) as All files.
Then try to unzip the files. You should be able to find par.bak file inside the unzipped folder.
BR,
Anurag