I have a little nail file spindle powered by a single AA cell from Walmart for about $15. It works OK in a traveling repair kit. With some patience, it will get the job done and there is little danger that you will injure a reed. However, it lacks torque and stalls easily. You pays your money and you takes your choice. ;o)
Vern Visit my harmonica website www.Hands-Free-Chromatic.7p.com
I use a tool made from a 2 aaa penlite. I replaced one battery with a camera motor. The switch is still the switch. The torque in inch ounces is so low that there is NO chance of injuring a reed. I use a sho-foo brownie. The collet is from a broken fingernail shaper.