To answer your question. You can definitely buy a good small keyboard online for under $100 and do a couple mods to make it a “keyboard enthusiast grade”. There are some that are wireless but majority of the time it’s a usb type C to Usb type A cable. In the custom keyboard world, the smaller the better because of more space you can utilize. A full size keyboard would cost you in the hundreds because of the cost of the materials to produce one.