If you were to post a photo of the carb it would help with it's identification, but from your description, it may be a Douglas carb. Douglas carbs had a rotary barrel rather than the normal throttle slide. Spares for Douglas carbs are few and far between, so you may have to resort to a mix and match of float and needle from other makes so that you end up with the correct fuel level. Even then you may need to do some fine tuning to get the engine running sweetly. The correct fuel level is usually set just below the point at which fuel continually leaks from the carb with the engine stationary - the induction then quickly picks up the petrol, making starting easy.
Hope this helps,
Regards,
Eddie.