Give it some time. Find out if there is a local newspaper for your area (usually a weekly, usually free) and check the ads in that and in any other local newspapers. Regularly check out thrift stores in your area. If you have the time, check out garage sales and estate sales -- especially those that advertise sewing items for sale. There should be a few estate sale organizations in your area that have online listings. These are very helpful as you can look through the photos posted prior to the sale and see if there are any sewing machines in the pictures. Here is one website where you can sign up to be notified of estate sales in your area:
http://www.estatesales.net/ .
You could also join the SewItsForSale group at groups.yahoo.com . Every once in awhile someone posts a vintage machine for sale. I think it's okay to purchase from eBay *if* the seller has a stellar track record (check their feedback history) and routinely sells vintage machines on eBay. People who don't routinely sell sewing machines on eBay often don't understand whether they actually work or not, and also often do not package them correctly for shipment, resulting in damage when they arrive.