The unit I have is probably an 80's model.
Raymarine in Belrose have parts for the later models which they think will probably fit, but cost nearly as much as a new one.
It looks like the push rod/tube is screwed on to the bushing then crimped.
Could be tricky getting it back on to the drive screw with all the ball bearings.
The unit was in very good condition and internally, belts etc. looks good.
I haven't been able to talk to anyone at Aquatronics yet, but in the meantime if anyone has an old unit they wish to sell for parts, let me know