Or all you have. So watch those plural words. But website and newsgroup promos can mention that your item is available in quantity. After your winner takes as many as they want, you then email your remaining higher bidders. Thank them for their auction participation and mention you just happen to have a few more of these on hand.
Most higher bidders welcome such an email.
But avoid emailing bottom feeders. Mining those bidder lists of other sellers is generally a no-no. But if you have an unusual and high ticket item up for grabs, rarely mentioning that it just went up for auction to those with serious interests might be appropriate. So, be sure to sell unusual sole source items. Offer only the items that you thoroughly know and understand.