Try the Used Market

Like all books ever published, The Cross-Time Engineer by Leo Frankowski should be available on the used market. If you're lucky, it hasn't become a collector's item (with the corresponding price inflation).

There are a number of useful sources for used books on the net, including:

Bookfinder	Search Bookfinder, a meta-searcher for used books
Advanced Book Exchange	Search for book
Amazon.com	Search for author