If you own an iPad with a Pianoteq license, and a CME WIDI Master for your Prophet, you can have a decent piano sound.
Alternatively, the 1010music Tangerine ships with a decent piano multisample out of the box - a USB-A to USB-C will be needed or a combination of WIDI Master and WIDI jack. As a bonus, Tangerine can auto sample your Prophet and record clips.