Hi CE, thanks for responding.
I was considering a HIghlander, but they require that you rout the bottom of the saddle slot, which is beyond my comfort zone. What I ended up installing was a DTAR WAvelength, another undersaddle pickup (distant cousin to the Highlander) which is somewhat similar but required no routing. I didn't even have to sand down the saddle bottom, as the transducer strip added no significant height to the saddle.
I'm still trying to decide what I think of it. It's certainly less woody sounding than the K&K I replaced, which I expected, and doesn't have the characteristic magnetic tone the M1 had. With a little more fiddling and eq-ing I can probably minimize the undersaddle sound. I'm confident it will be better in louder settings, ie., much less prone to feedback than the K&K.
Bill