The Roland PR-300 is long gone, but its little brother carries on.
This MIDI player players floppy disks using the GM/GS Voices built in to play SMF files...and Roland Format Files. It will not play the organ....but the organ may play the MIDI Voices in it, just as you were able to do with the PR-300.
One MIDI cable is needed from MIDI OUT in the ORGAN for you to be able to play these voices.
Two MONO 1/4" Plug to RCA PHONO Plug cables carry the audio sound from it to the organ.
You can carry it with one hand, and use a USB ThumbDrive in place of floppy disks at home or other location using the internal speakers.
This is not available from Rodgers dealers....though it should be.