No. Nobody has them or sells them other than S&W. S&W does not 'sell' individual spare parts for the 15-22, but they will sell/send you a replacement part if you 'break' one of your parts or they if a part fails.

You have to call S&W directly and tell them you messed up your upper.

Since the lower is considered a firearm, you won't have any luck getting one without buying a whole new rifle.

The upper can be had. A forum member here broke his upper and S&W sold him a new one for ~$26.