Put a wanted ad on Armslist, you'll be shocked how many vendors will respond.

armslist.com/posts/472830/charlotte-north-carolina-handguns-for-sale--smith---wesson-model-610-10mm----40-cal---rare--model-year-1990

Kit, this will be difficult to find. You should start with some if the online gun and auction sites such as Arms list and others. There are a few rare 10mm's I have found by checking out local pawn shops as well. members tend to find things in the for sale sections of gun forums as well.