Here are some nice megillah cases that come made to order in various sizes all the way up to 25 inches. The tube is wrapped in a polished leather with a nice sheen. The top and bottom are made of hard wood. These cases are locally made in the New York area. They are more expensive than many of the megillah cases that you will see in Judaica stores, but they are far nicer, the difference is like day and night. Please call for a price on any of these cases. Measure your megillah before you call so I can provide an exact price.
This megillah case is designed for a large 20 inch megillah. This style and size is $175.
Here is a closeup so you can see the details.
If your megillah has an eitz chaim this case would be a good choice because they can hold a megillah up to 25 inches. You can also or an eitz chaim for a megillah ($130).