You can find putlog coupler suppliers globally, from large Chinese manufacturers like Wellmade, APAC, and those listed on Alibaba.com (offering custom/wholesale options), to US suppliers such as Ver Sales, Kee Safety, and Lynn Ladder, with regional providers like Sparsteel in the UAE, offering various types (pressed, forged) for different scaffolding systems. Key suppliers include both specialized scaffold companies and general construction suppliers. 

When choosing a supplier, consider the material (galvanized steel is common), finish, compatibility with your tube size (e.g., 48.3mm OD), and compliance with standards like BS 1139.