A MIDI controller is any hardware or software that generates and transmits Musical Instrument Digital Interface (MIDI) data to MIDI-enabled devices, typically to trigger sounds and control parameters of an electronic music performance.
a link to a site with some midi controllers with pictures and prices in USD. https://blog.landr.com/50-best-midi-controllers/
If you live in the Netherlands you can find a lot of gear on the Dutch version of Ebay; Marktplaats.nl You can mostly find midi controllers for a good price here. Second hand and new.
If you are new to this and you feel like needing one you can for instance find a little midi controller with keys, pads or knobs like the Korg Nano series starting from 20 euros second hand. Of course you can go up to much higher prices and more advanced controllers, but there is no need for that in the beginning.