Holz no longer makes one.
Timbersled no longer offers just the plate.
Two options.
Vanamburg eng may make one still... a bit pricey @ $175
Not on their website but give Mike a call, talk to Mike directly... (509) 225-6681... Call early its Friday.
OR you can make your own... just like the Holz.... which uses the Poaris Edge steerig post bearing [ part numbers 5133648 (qty 1, housing) and 5432785 (qty 2, bushings) and a zerk fitting 7080510 ] and a piece of angle aluminum cut to size... you could have a local fab shop press-break you a piece.
Here is a pic of the Holz part. I'd probably extend the plate back a bit more to use the second set of tapped holes in the steering hoop.
BTW... do you ride the Hurley in BC?