To duplicate the car, u have to bring the original (but u already lost it), or if you keep the serial number at steel tag that attach to one of the key, u can give the number to Perodua then they will duplicate a new key to u. But you have to pay around rm200 if i'm not mistaken. Or u might try to ask your finance if they got the spare key for it. Usually finance will hold one spare key for 'tarik' purpose if you fail to pay ur payment. Try ask from them although i think i'll not be easy for you to get it from them. The last option is like Tohsan said. Change all your lock, but u will loss security features that have in original key (smart key, wut ever la), and it's also no cheap to change the lock i think.
If i were u, i'll try to call Perodua and ask them what they can do to help first....