The US is one of the only countries using the Imperial SAE sizing system for nuts, bolts, screws, washers, etc. The rest of the world uses the metric system. Metric sizes should be abundant and CHEAP! I found otherwise looking for exact types & sizes for an import auto restoration project. I also learned the hard way about hardness grading.
Shanghai Jian & Mei Industry and Trade Co., Ltd. is the company which manufacture and export fasteners and metal hardware, founded in 2006, with import-export authority, and the office is located in Shanghai –the Economic center of China. In order to improve price competitiveness, we invested and shared several factories during last fifteen years. This makes us have the capability of supplying many kinds of fastener and hardware. We could supply one-stop shopping service, saving our clients many purchase cost and make them profit maximization.
https://www.jm-industry.com