If you live in the States, you should consider visiting the Harpsichord Clearing House (www. harpsichord.com) in Massachusetts. The have a gallery of used keyboard instruments, including modern harpsichords, clavichords, and fortepianos, as well as historic instruments. In addition, you should consider visiting the Boston Early Music Festival. Besides the concerts and lecture recitals, many builders rent booths to display their instruments for sale. Best of luck in your search.