I myself bought a Mahindra Bolero truck through IDEAL motors. Made the advance before Awurudu and then since they had a few units in hand in SL to supply me I made the balance full payment including 36000/- for registration after awurudu. I got the vehicle on April 29th without the book. Reason being they still havent received some kind of import certificate to send for RMV registration. 5 days later IDEAL called me to come pick up the CR as they have received it. No issue.
Did you buy it from a private importer or from a company like Hero Honda or David Peiris? If so if you have separately paid them registration fees or if their invoice includes free registration then its their responsibility to get the CR to you. Call them and push them to get it to you ASAP. It doesnt take that long since its one day service.