Using sampler with CDJ2000nxs2 or MIDI mapping?

I own the pro nexus setup (two CDJ-2000nxs2 and a DJM-900nxs mixer) and also a Novation Launchpad MK2.

I am trying to figure out a way to somehow use the sampler in Rekordbox with my gear, as the CDJs don't have the performance pads that are common in controllers. I was wondering if anyone knew how to MIDI map the sampler to be used with the Launchpad? Or if there is any other way I can use the sampler with my gear?