I think one good combination would be using Musette(French Accordian), I presume the 7000 has that. And mix with a mellow drawbar setting using the even numbered footages like 16,8,4 maybe 2. Try different combinations of those drawbars. If my memory servers me correctly the organ sound was more or less a straight tone with no leslie, tremolo or vibrato effect. Maybe vibrato, but then I don't know if you can put vibrato on an organ sound on your keyboard.

Scott