I don't like the small stuff that takes small button batteries. I can buy a package of AA's for what two or three of the button batteries cost. They're neat but... I don't see them having a very long run time. You might want to try a LED Head Lite for after hour keyboarding.
I prefer AA's then AAA's. I have rechargeables and a solar charger for when there's no power.
I admit I have an INOVA Microlight (takes BIG button batteries) but it's just for fun. It does not go on a finger.
http://www.inovalight.com/microlight/My mini MagLite is my main disaster light in my BOB. I upgraded my mini MagLite to LED so it runs even longer now but the beam doesn't focus as well as a standard bulb. MagLites are rock solid.
http://www.maglite.com/AA_Cell_LED.asphttp://www.maglite.com/product.asp?psc=2AACELL&pt=RNiteIze makes a headband for small AA flashlights.
http://www.niteize.com/products/headbandThere are several single AA LED lites out there. Gerber makes some; they bought out CMG which had a nice lite.
http://www.gerbergear.com/index.php/product/id/7It's just some suggestions. Have FUN!