I have done a bit of research and read a lot of threads concerning the 260 bucket. 16" is the largest I have found that is commercially available. Now, on the GTT there is a thread on a "Ditch Cleaning" bucket with build diagrams that someone made.... It could be modified to your application. I don't remember the exact size. Now, there are several opinions out there that anything bigger than the 16" could possibly stress or contort the Dipper stick.