comments:
https://www.amazon.com/8-Pin-Triple-Sustain-Pedal-Digital/dp/B0GY9D94L4/ref=sr_1_33
From the manual for the HP3 or HP7 there were 2 different pedal setups. https://www.manualslib.com/manual/314719/Roland-Hp-3.html?page=7#manual The HP7 uses a 7 pin plug with a center guide slot that might be considered as a pin also. It allowed for half pedal changing amount of sustain which probably required a rotary control in the pedal itself like a volume control pot. The HP3 used a 3 conductor stereo style 1/4" plug as it did not have half pedal sustain, only on or off sustain. If you have the 8 pin style connector maybe you have an HP7e piano? Here's your best bet for what you need: https://www.amazon.com/8-Pin-Triple-Sustain-Pedal-Digital/dp/B0GY9D94L4/ref=sr_1_33I would be surprised if it was different, but if so you would have to get into the pedal and switch some of the wires around.