JJB Electronics uses an approach similar to K&K but much cheaper. I have their Premier 220 (2 pads) ($40) in a beater travel guitar and it sounds pretty good plugged in via a Fishman preamp. It sounds ok without the preamp but it's better with it, and I prefer to have some control over the vol, EQ, etc. Had it installed by a luthier for $30.

Here's a sound sample I did for someone on another forum looking at JJB, other options. https://soundcloud.com/vern-equinox/jjb-220-sampler