I think there's a lot of 'depends' in the answer.
If you're talking about a shaft/coupling/paddles combo, go to a local metal fab shop and sketch it out with them. Might need to consider torque issues too. dunno what you've got in mind for bracing/seal/etc, but if it's just a 3in TC fitting, clamped, etc., any robust motor would make short work of it. Gotta keep it sealed (assuming it's a still, not a mash tank) and keep it from spinning.