The Ridgewing guitar’s basic pickguard is 2.5mm thick piece of acrylic plastic attached to the guitar with three M3 machine screws. This makes it as easy to swap out pickguards as any other part of the guitar.

You can laser-cut this plastic at your local hackerspace, or stink up your shop using a band saw, or sweat a little with a coping saw. Just leave the surface protection on until you are all done filing and polishing the edges. Drill the holes with spur bits.  Regular drill bits can split the plastic.

To complicate matters slightly, the pickguard blank has to be heated and bent a little like a potato chip to clear the grills. You have to get the plastic heated up to about 105ᵒC (221ᵒF), just over the boiling point of water. A shop hot air gun does this pretty quickly and easily. However a standard hair blow dryer only gets up to about 55ᵒC (130ᵒ). I imagine that in a pinch holding it over a little campfire might work.

There is no reason to stick with plastic for the pickguard.  Why not a steam-bent piece of rosewood?

Or carbon fiber?

Or if you have an old bucket and some tin snips –