Another really good walkman to get is the WM-2 (Walkman II) : the second walkman. This is the walkman that set the world on fire and made EVERYBODY want to get a walkman! It was released in 1981 and rather than selling 15,000 per month they sold about 25,000 per month for five years (1.5M total) despite the high ($140) cost!! It comes in grey (most common), black (2nd most common), and red (most rare). like the original TPS-L2, it has a "hotline" button but this time it was moved to an orange button halfway down the headphone wires. The "hotline" button makes the cassette player literally PAUSE playback (it didn't just lower the sound), which was better than the TPS-L2. The headphones are hella expensive so I would recommend the "Koss Retrospekt" headphones as a very high-quality alternative in the same spirit as the MDR-4L1S headphones of the Walkman II.
Thanks for explaining the hotline button! Will add it to WML. Did you know that it was released in a 4th, arguably even rarer, color? See https://walkman.land/sony/wm-2