Hhhhmmm, that's going to be a tough one. The Harberts come up periodically, but usually only a handful a year give or take. If you're located in the states you may try feeling out some people across the pond to see if anyone has a lead. My guess is that if you're asking here that you've been trying several other sources and are trying to get as many feelers out as possible. Pretty slow around here these days, but who knows, you may get a pm from somebody wanting to sell one. Sometimes to score something like that via the internet these days you've go to have some significant report with trusted collectors. Have you gone the facebook group route and asked around yet?