anyone know if there's such a thing as a mechanical angle gauge (aka "two arm protractor") but with very short arms for measuring angles on small objects? needs to be able to measure both acute and obtuse angles.

the notch disc style ones are a perfect size, but only allow you to match fixed sets of angles so they're not very useful if the angle isn't a round number.

specifically looking for a mechanical tool - I don't want anything digital, I really hate needing batteries in stuff like this.