Hey, I honestly took for granted the electric die grinders from Sears was still available. My bad.
Bought mine 20+ years ago.
In hindsight, unless you rig a footpedal in series to vary rpm............you're better off saving your $$ and getting a small compressor and a pneumatic grinder for porting. The sears unit I have has overrev'd my bigger cutters to the extent that they have bent them.
Bottomline: Home porting can be done cheap and, with a common sense approach, it'll add HP and not kill your TQ.