Check for estate sales in your area. You can google it and find out what will be either auctioned or out-right sold. I have seen some great deals on machines that way. Also, if your church has a bulletin paper it would be a good place to put an ad for what you are looking for. Any place where seniors meet, or tell the people at the secondhand store you are in the market if any come in. I once saw a man come in to pick up a almost new Juki for a fraction of the normal cost.
I think my point is, don't limit your looking to normal sewing guilds or stores.