If you're only going to use the tool for slotting cartos, you can get a 'rotary tool', dremel knock off, from Harbor Freight for $25. I don't recommend their tools for real work, but slotting cartos, no problem.
I looked at those but didn't like the rating so I bought this kit for $39.99~> Wel-Bilt Rotary Tool Kit 131-Pc. So far I'm very happy with it I really like holder and the flexible shaft..I will use it for other things besides slotting e cigs..looks like it's on back order right now though. I'm sure it won't last forever either but for $40 I'm sure it will last long enough..also looks like you can replace the brushes in it if they wear. If someone is only going to use it for slotting it's probably a good idea to buy that harbor freight $10 or $25 kit..but they get really bad reviews.