Well for 523 Euros plus shipping you can have a new one:
For $63 and nearly $100 shipping (depending on your location I suppose)
There is this low mileage example:
And if you have a look here and scroll down there is a list of other bikes the same hub was used on which includes CB450 K1 and K2, CL72 and CL77
I've never heard of relining a brake hub as you've described, but I'm sure the correct part can be made. I'd assume the relining process would be similar to replacing a cylinder sleeve. I remember reading how Alan Millyard created a 4LS front hub from scratch for a replica Honda racer, he added his own iron brake linings to a fabricated hub so it certainly can be done.