I have these as a trial to see if they work. They can be soldered, seem accurate, are cheap(2.50GBP) and will be available soon. They are based on the dimensions of the BWA bracket which is unobtainable these days. Like the BWA bracket they are short. ie the motor plate is close to the axle centre line so so fiddling/fettling is required.
Thanks for the response, David. I have been in contact with my friend who is making these and intend to get some made with longer "arms" for perhaps a sports car chassis and also creating some with an "offset" although a rat tail file should be able to sort that.