Compiler Design in C is now, unfortunately, out of print. You can often find used copies on the web. (Try Alibris, Bibliofind, BookFinder, and Half.com.) You can also read Andrew Schuleman's review of the book.
Get the source code by clicking on the following link. Bear in mind, though, that this code hasn't been touched in several years. It will undoubtedly require some massaging for your compiler to accept it and Allen can't really help you with this process.