Clutch Master Cylinder Rebuild Kit

I am wondering what people are using to rebuild their clutch master cylinder?
The OEM kit is MB870513 and this is no longer available.
There doesn’t appear to be an aftermarket alternative available, currently.

I rebuilt mine some time ago using the insides from a LHD aftermarket cylinder, and, yes, you can still get one of these, for now.

This is the sort of thing that will take our cars off the road very quickly indeed. The OEM one’s are fragile and split easily.
The aftermarket one I stripped was far superior, and will probably last for years.

Has anyone been able to find a source of any kits?

I am considering trying to get some made, but wanted to see if anyone had a solution?

Many Thanks