I'd also vote for software. Even if you don't want to RELY on it, you can use it as a fast reality check. If it disagrees with your hand reduction--you know there's a problem somewhere.
Used Palm IIIxe PDA, $25. John Manson's "Navigation" suite for the Palm, probably another $25. Great little combination and yes, it can be used on older and newer and fancier Palms as well.