HI guy's, just seen this, "spose" it could help somebody in the future...
similar problem with my J head.....luckily I live in a converted water mill.......found a 10" dia castiron sloose wheel......u know the sort, u turn it to close off the water etc etc (normally fitted to an Acme threaded rod)....anyway made an adapter flange and ST/ST knob and use that insead of the original type lever...held on with a socket head grub screw...... the wheel weigh's around 3-4 pounds and gives a defenite smooth (flywheel) solid feel when using the spindle, loads'a control and it just goes round and round......so u don't have to move the lever around the spindle for that extra 1/2" of travel u always need !!!!!....
have recently bought an original lever, found it to be a right pain in the arse when drilling......it's now in the bottom of the junk cupboard soon to be followed by the original contactor/control box, complete with it's contents...should say it a 1996, Adcock + Shipley J head, 440v....
have a good 1.......Clogs.....