@talentryto- Kitchen specialty stores are the best places to shop for oven thermometers. They usually carry a wide variety of all types of kitchen thermometers in stock, so more than likely you will find exactly what you need.
Another benefit of shopping for oven thermometers at a kitchen store is that you can see them in person to familiarize yourself with their features and quality. This is impossible when you shop online.
Some areas don't have kitchen supply stores, but most cities and larger towns do. Though you may have to travel a bit of a distance to find one, if you need specific types of oven thermometers the trip will be worth it.