An old C-series Electone might be wide enough...the A-series and maybe the B-series may be a bit too narrow, although some of the latter were quite wide.

Here is the Electone museum...many, but not all, of the older series organs are pictured (some with several pictures...click on IMAGES>>> just under the top part and at the right of the main picture) with specs, right up to almost the present, many have the dimensions listed.

http://www.electone.com/museum/

Looking at the history, I actually owned several of those listed, and played almost all of them. I like visting this site once in awhile.

I hope this helps a bit.

Probably the most likely ones to find and use would be the C-series in the 70's.

Ian