Non toxic low melting point alloy
I'm not a metallurgist, which you should probably ask... but there is this that I found:

Low Melting Fusible Alloys

Both Cadmium and Lead are toxic, but Bismuth, Indium, and Tin are not. An alloy of those might be what you're looking for. Indium raises the price-point considerably, as it's a few magnitudes more expensive than Bismuth and Tin.