Most people here tend to recommend the DIMMEST red light you can get. The dimmer the better. Personally, I have one of those headlamps the a lot of people, especially at star parties, detest. But I've covered mine over with red fingernail polish so that it is very dim.
That said, there are two adjustable hand held flashlights you could look into. They are both similar but put out by two different resellers. One is by Celestron and the other that I know of is put out by Orion. Both have a dimmer dial so that you can bring up the intensity when needed and get the light as dim as you need.
Check 'em out!
I use a Petzl head lamp myself. It comes with a red flip cover, but it's still too bright so I bought some red brake light tape at an auto supply store and put a couple of extra layers of tape over the cover. I also try to use weak batteries.