Chances are, it may have been uniquely made for the promo.
As for contacting Sierra folks (the company is pretty much “defunt” – or the Sierra that would know and/or care about Manhunter, or any of the classics). Your best bet would be to head to the Sierra Help Pages (www.sierrahelp.com/forums) and ask on there… Plenty of knowledgeable people there that may be able to assist.