Saw this, and figured someone here might find it useful...
http://cgi.ebay.com/Turbo-Grafx-16-Hu-Card-Convertor-US-Japan-DUO_W0QQitemZ170181518563QQihZ007QQcategoryZ187QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
HuCard Coverter, they refer to as the Purple Barney Converter.
Useful but pricey - installing a region switch is the better option (says the dumb-ass using a converter).