I am looking to upgrade the optics on my B&L 4000. Problem is the threads on the back of the OTA are smaller than any of the makers currently in business. So I am looking for any of the accessories that may have come with this scope new. Such as a Visual Back, Star Prism, Camera Adapter, etc. I need the locking ring that fits the threads on the back of the OTA. Any help or ideas are greatly appreciated.