Rear brake master cylinder/reservoir

Just started to strip down the seized master cylinder and have found that the nylon retaining collar has been glued in!!! due to a broken casting on the retainer, upshot is I'm in dire need of a replacement, don't mind if it is a bit rough as I have a rebuild kit and the replacement part will sent away for powder coating it just needs to be servicable. I'm doing a ground up resto and trying to keep as many OEM specs as is possible.

that nylon collar has two retaining lugs that have to be pressed in through holes either side of the aluminium body

Truly a coincidence.........I literally just finished making one for my current project.  1/2" nylon ( kitchen cutting board).
Took less then an hour and cost nothing.  Should be self explanatory.
 
The original had 1 lug missing
 
 
 
 

Looks good, but I think I didn't describe the issue correctly, the previous owner had glued/araldited the housing, so when I went to remove the retainer the housing ring with the notches in it came off., so unfortunately I need to replace the whole housing,(which as luck would have it I've found on Buyee Japan) but thanks for replying , its good to hear from other big 6 fans.

If you search with this reference there are several units for sale.

KAWASAKI PARTS 43022-1003