Most clubs will have RekordBox-ready CDJs, especially in Europe. It can be older models (850s or even 450s adn 350s), but they should all take a RekordBox USB stick. I usually carry a stick with me just in case.
iPad would not be my choice as it’s a lot harder to match up with anything.
A laptop running RekordBox DJ or Mixvibes Cross or any other DJ software with a wide Pioneer HID support will work as well. Might need to bring a portable powered USB-hub and a few USB-leads and your laptop stand, but that should elevate a CDJ setup and give you some control in your DJ software.
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