Nope there is no such alternate (wish there was) but unfortunately you will have to go for FIR and then follow the procedure that you already know. You will be issued a duplicate book.
I lost mine as well, and had a duplicate issued. Fortunately or unfortunately i found my missing original book. Went to ETO's office and they told me that the original has been discarded and there was no way to cancel or discard the duplicate.....
so re-registration and other processes are not there.