in a pinch or a onesie setup - many have used a dremel-type tool that is held in a hose clamp or a u-bolt hold-down fitting onto your compund. use whatever clamping arrangement necessary even up to cutting a special wood block to sit on the compound and hold the tool housing firmly.
although its hard to get the dremel stone exactly perpendicular to the lathe axis- it isnt needed to be perfect to get the desired result.
the grinding pressures are supposed to be very moderate so the tool pressure onthe mount should not be a problem factor. use coarse stones and watch for glazing, dress them often and do your setups and measurements carefully. even a coarse stone will gibe a failry fine finish on a rotating shaft and you can easily hone the shaft the last tenth or so with a handheld stone once its ground to size
otherwise, you can use a sewing machine motor and their accompanying belt drives and parts, make a few speed reducing or increasing pulleys if needed and mount the stones directly on a drill rod axle or use an arbor-type tool ( think mill holder with a setscrew) to hold a mounted stone. take a small motor mounting bracket and mount the motor onto it and use the extra space to hold the secondary axle in a dual brass bushing or a skate bearing arrangement. simple setscrew collars to hold the shafts in place. easy to make a cone pulley for speed changes when using the round rubber drive belting or even the angular vee type.