Carb linkage problem

[firehawk]

I'm having a bit of trouble with the carb linkages on my engine. First of all, I only have one linkage rod which attaches the arm to the carb, and second - it only has one intact ball joint.

I've been hunting around town and went through several websites looking for suitable replacement parts but they are nowhere to be found. The ball joints are a weird combination of female M4 thread to the rod and male M5 to the arm. Strangely, the rod also has right-handed threads on both ends so one end needs to be detached for adjustment. Without the ball joints, the rod itself is 80mm long

Any ideas where I could find suitable ball joints or complete rods?

Edit: Apparently aircooled VW:s and Porsches use similar linkages for downdraft IDA/DRLA carbs.