Worthpoint and other web sites have listed that model or similar models for sale, and at least one had a manual.

You might try contacting a seller, and ask to purchase only a copy of the manual. Check eBay.com and other sites using Google.com to search.

Examples:

https://www.worthpoint.com/worthopedia/8mm-cine-projector-editor-camera-500351825

https://www.worthpoint.com/worthopedia/matahari-model-116-8mm-silent-cine-1112181970



https://www.worthpoint.com/worthopedia/8mm-cine-projector-editor-camera-500351825