Look for 'pin chuck' or 'pin vice' on eBay or similar. At least, that's what I've always known them as.
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I have a few, including a couple with wooden handles, obviously never intended for an eggbeater or power tool. The best made ones are Eclipse brand. The Chinese cheap sets of four in a wallet are... cheap. I've thrown one out from my set as it was so off centre it was impossible to use, yet I kept picking it up by mistake.
It's worth saying that Proxxon equivalents to Dremels come with 0.5mm drills included, which fit directly in the Proxxon chuck. There may be a 1mm too - can't remember now. I had a B+D one, which caught fire. I now have a Proxxon which has taken a lot of abuse and still works very well. You can also get the chucks for them as spares.
If you rest a large drawing pin in the back of the chuck shaft (should be hollow), you can use it in the palm of the hand like a jeweller's screwdriver.
