Peugeot is known for those tiny little steering wheels so that's understandable. We can't recommend something specific that we've tested, but we'd suggest looking for a lock that stretches to fit the wheel's shape rather than one that clamps on in a set position because, like you say, the 308's steering wheel also isn't a traditional shape. I'm not sure which ones you've tried but Streetwize is a reputable brand and this steering wheel lock might work, it's also well-reviewed: amzn.to/3aL7AYX