If this is a PTO coupling, 6 spline shaft, then you should be able to get one from a farm equipment supply. But if memory serves me right I though the large size was 1 3/8 not 1 1/2.
Where can I find exaples of diagonal brace layouts for scissor
trusses. My application is Agricultural so I have 4' spacings , no ceiling, and metal cladding. All examples I find refer to diaphram on top and bottom, I don't thing this applies.