I don't know if it's still available but there was Castor formulated for model airplane use from a company called Sig. It came in one quart cans at the hobby shop. That was a few years ago so I can't say if its still out there. I've used medical grade Castor but only added about one ounce to a gallon of 2 cycle mix along with Opti-2. You still get that great smell but there isn't enough Castor to foul things up. Good luck. Let us know what you think of the smell.
In all honesty, I would guess that those of us who really like it are associating it with our youth and whatever activities we were involved with that saw Castor oil used. It might not smell that great to just anyone