Try Fischer Engineering Co., Dayton, Ohio. www.fischerengr.com. They manufacture several different types of bend testers. They are rather expensive. A very useable coupon bender can be fabricated using the specifications in AWS D1.1. Refer to section 4.8.3 and Figure 4.15 for measurements for standard thickness of materials. If the metal is thicker than standard the mandrel diameter is four times the metal thickness. The Die part would be sized accordingly, allowing for metal thickness. A hand operated hydraulic press could be used for power.
Hope this is helpful.