In my opinion, and like some said in the comments above, the standard airsoft version is the best quality / price alternative to any collectible -and overpriced- prop one could find. It's really decent looking, and you can eventually shoot it. Go for it !
For instance, I bought an used airsoft M41A (the one you can find on Evike) and built this wall-mount out of wood and metal + USCM patches (I did a little paint job on the gun, but not much).
It cost me less than 250$ for the whole set, and it does the job as well as any HCG wall-mounted prop.
I wouldn't hesitate a second if I were you. And don't forget you'd save money on the 400$ budget, with which you could buy a gift to your wife. So everyone wins !