Well, personally, being a wood worker, I think all knife scales need to be made from exotic imported hardwoods, like Paduak or Bubinga.

You could scan it, but unless you have somebody who knows what they are doing, it'll be a difficult first step. That said, this is a simple shape, and is probably a good one to learn on.

But take a look at the shape of the scale. It's pretty much a 2d shape, with a few 3d features to it. This is a great object to start modelling on.

I am biased towards Sketch up, but I'm assuming most modeling software will have similar features that will allow you to do the same things:

I'd start by putting this and a 6 inch ruler on a scanner bed ( like a photo/document scanner). But have a ruler that shows mm, as it's much easier to 3d model in metric. Make sure the scale's outline is sitting flat on the scanner bed.

Import that picture into SU,and then trace along the outside edge of the scale, and probably the holes too. Then resize the whole thing based on the ruler that's in the picture too. Now you have the outline of the scale, to scale. You can then extrude it to the correct thickness, and add the features you want.

It'll take a bit of practice if you've never done something like this before, but you'll learn a lot.