Even though it's been a while since you guys started this thread I wanted to share something that works nicely for me.
I purchased a 3-key USB keypad for $16 form Amazon https://www.amazon.com/dp/B08P1GY3GN/ref=cm_sw_em_r_mt_dp_H610W0ZBZ6DNXZSZESYK
Easily programed the keys to be F2, F3 and F4 and it works like a charm on my RPi arcade.