You could try a really deep cornet mouthpiece (like a Wick 2) and used it with a trumpet adapter. The intonation might be a little squirrley, but for a change of pace on a tune or two, it might work. I don't think it would be the best thing for all-around trumpet development. I don't know the what level your student plays at, but if he's pretty young, staying on whatever mpc he already uses might be best. The ear and a really light approach may be best in that case.