This is an excellent $15 wireless keyboard

I bought this $15 keyboard (Amazon) last year to use with a Raspberry Pi (mainly to play Wizardry: Proving Grounds of the Mad Overlord using the DOSBox emulator). Now that I've spent the last year teaching myself to touch type, I've come to like it more than my wireless Apple keyboard. (I remapped the keys, as shown here. Still not entirely happy with the remapping, but I'll try Karabiner next.) Note: it's not Bluetooth, so it requires the use of a USB dongle.