KC strings (
www.kcstrings.com) make an extension that you don't have to cut into the scroll to fit the string, nor bend the string around the side. You can order it from them and have a good luthier install it locally. You can decide how many gates you want for the semitones and they're very easy to adjust yourself. I'm really pleased with mine.
Alternatively, if you can get your bass down to Roger Dawson in London he has a good reputation for making extensions. I've never met him, but I know a couple of people with his extensions.