Instead of selling using the "auction" format as you currently do, you need to list at "fixed price".
For more information: http://pages.ebay.ca/help/sell/fixed-price.html
You can either:
1) have one listing with a quantity of 1,000
2) reduce the quantity to 800 and offer a second listing with 20 lots each containing 10 items
3) any other combinations you feel comfortable with.
It should be noted that about 90% of all listings on eBay use the "fixed price" format because this is what buyers prefer. The "auction" format is going out of style in most categories and accounts for a smaller percentage of listings, year after year.