Be glad that your arm isn't one of the articulating arms, because they cost 2 legs and 3 arms to buy. If it is the articulating arm, then you have to buy the complete assembly, since no service parts are available. I know that I couldn't find anything in the aftermarket for that arm when it failed. Only a new one from Curtis, who is extremely proud of their service parts. I believe that Mikes picture shows an articulating arm, and I am basing that on the image in in the reflection on the glass.
The cab on my BX23s has a single bolt and nut that holds the wiper blade to the non-articulating arm.