Value means nothing to me...... heirloom means everything to me.
The only reason I would purchase other wood is for gun fit.
I've been trying to stay out of this one, but I just have to throw in my two cents. The Browning 42 is a very nice gun but it's not all that special in the overall scheme of things. Do what you want with it. If you must turn it into an "heirloom," the most tasteful way to do it would be with an engraved grip cap or butt plate, and the proper cap will have plenty of room for a professional engraver to work his/her magic. Don't limit your search to the commonly available caps. I get the sense that you are trying to laser-etch the wood as a DIY project and that's why you are not wild about the grip cap idea. Find a cap that can be fitted to the gun with plenty of flat surface area and take the cap to a professional gun or jewelry engraver. In the long run, that will probably make the kid happier than a carved stock. An alternative would be to have the receiver professionally engraved and reblued. Not reversible, but more tasteful than mucking with the wood.