I don't know about a brush guard, can't seem to locate any for a 345, but theres a bumper on ebay listed at $55.
http://cgi.ebay.com/JOHN-DEERE-FRON...ryZ82248QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
http://cgi.ebay.com/JOHN-DEERE-FRON...ryZ82248QQssPageNameZWDVWQQrdZ1QQcmdZViewItem