which drum sampler for live use?

Alesis Trigger I/O or a Roland trigger-to-MIDI converter. Connect it to a laptop running the software of your choice.

Either that or invest in an old hardware sampler (do they even make hardware samplers anymore?), but you'd have to do some research as to what would have the capability to play back across multiple channels that you'd need. And even then, you'd still need to convert the trigger signals to MIDI to work with the sampler. Akai and E-Mu were the big hardware sampler guys back in the day, but it's been years since I've even seen one of these things.

There isn't a cheap dedicated drum brain that allows you to upload your own samples. DDrum does this, IIRC, and maybe the Alesis DM5 Pro, but I'm not sure about the latter.