Yes, thats the early Plus 4 set up on a 3HA axle
Was able to obtain a spare lever from Derek Willburn but I think it was the last one he had.
Derek stepped in just before I sat down with my Girling parts books and tried to cross reference it
It may be Riley RM but I'm not 100% sure of that.
Won't be an easy part to make - as its, profiled, twisted and then hardened and ground.
Could yours be welded? Not sure but I guess there are some on here who can wield a TIG torch better than me!!
Arwyn