Thats one of the early one's by the look of it with no colon between the hours and minutes probably a dot display too, watches with Hughes 29mm modules come up quite often on Ebay so keep an eye out for one with the same button orientation as yours....
Here's one with the module you need - http://cgi.ebay.com/Vintage-1970s-Compu-Chron-CompuChron-LED-Wristwatch_W0QQitemZ270527067007QQcmdZViewItemQQptZWristwatches?hash=item3efcab737f