Sorry Daniel - missed the rackmount requirement on top.
As rack-mounted drum modules declined in the last 15 years with the advent of softsynths, the trend has been to turn them into more user-friendly units to place on a drum kit with tons of usable sounds. I think drum triggers evolved into either units that attach to drum hardware and feed a MIDI module, or are an all-in one.
I'd look for a good used D4, D5 or DMPro to use as a trigger and pair it with your favorite rackmount sampler that you can easily get your WAV files into. Only cable from the kit will be a 1/4" from the pad to the back of the drum trigger unit.
there are some devices that are a self-contained MIDI trigger pad (the old Boss MPD-4), but then you are setting up a wall-wart power plug and a MIDI cable - i'd go trigger and sampler route.