WE have found some white and crystal antique doorknobs that we would like to use. Except we have a problem in this. These connect to each other with what appears to be about a half-inch square rod that is about three inches long. We do not have the internal mechanisms that connect to the door. Unfortunately current available ones will not work. Where can we find or purchase necessary parts to be able to use these fine antique doorknobs?? Any help or advice would sincerely appreciated. Thank you!