You probably need to be talking to these guys ?

https://robbreport.com.au/motors/au...e-McQueens-Metisse-Triumph-desert-racer/
http://www.metisse-motorcycles.com/part/

I'd be surprised if actual blueprints were available ?
The usual tactic is just to find what ye want, and make a jig from it to make a copy.

I've known of skilled folks to just generate the required dimensions from a photograph, and
working existing components into a chalk outline on the floor !
Thats how the design may have been arrived at in the first place ??

[Linked Image from robbreport.com.au]
[Linked Image from metisse-motorcycles.com]