Chuck,
I'm not sure if you're looking for the design that was on the side plate, or a way to replicate the side plate to fit the inlet in the wood?
If it's to replicate the side plate to fit into the inlet;
Take a picture of that side of the pistol with your digital camera.
Then with your computer and printer, crop and re-size the picture so the side plate image is the exact size of the inlet.
Print out the picture, then cut out the side plate inlet image.
If you can't do the cropping and re-sizing on your computer, measure the exact length and width of the side plate inlet, download the picture to a memory stick or disc, and take it to Kinko's or your local printing business and let them do the re-sizing and printing for you.
Glue, or draw the outline of the cut out side plate image on a suitable piece of brass, silver, and cut/file it out.
John