Since .ttf is vector and scalable, you just mean something that has a 9:20 ratio (or 3:6.67 )? I assume 9 is the width and 20 is the height?

I would suggest browsing those free font sites looking for something tall and thin, and just try them until you find something that fits. You just need to find something that's a bit more than three times taller than it is wide, right?