TubeNet

I have four of their mouthpieces. Really wanted to find a stainless I liked better than the SM3, but never did.

I just put an SM 3.5 along side several G&W mouthpieces. The E-2 is the closest in cup width and depth, and might be the one to try.

The Loud LM-20 is fairly similar to an SM3. I preferred it and used it for some time. (Eventually settled on the classic Wick 3AL.) Not currently in production, you'd have to find it used.