highland145 has the right idea and I will add to it. A lot of window manufacturers were local, stayed in business for a number of years and then were gone. What this means is that you need to find a store in your area that may have these parts in stock. If these windows were popular for a number of years, parts may still be around.
For example the slider in our condo was manufactured in Florida by a company that is no longer in business. But a company on the other side of the state has every component that can wear out as well as handles and the like for it. I wouldn't expect to find these parts in the midwest because the company that made the slider did not sell their products in the midwest.
Sometimes, the Internet is not the answer. You may even want to start at your local hardware store asking the oldest guy in there if he knows where you might find that latch.