That's small and inexpensive but I imagine with knitting and being on the finger it will be moving up and down creating a distraction...also I don't think I could knit with something on my finger like that.
I have asked a few sellers on ebay if I can get these in time for my trip, they aren't too expensive, under $15
Booga Bag & Fetching
I suggest checking at your local auto parts retailer(even Walmart's parts and accessory dept.) and look for one of the small map lights. The kind with a flexible stem, they are powered via the lighter/accessory sockets in your car. Just bend it to point the light where you need it. It will also come in handy if your DH needs to see his map. Other than that I would suggest one of the "snake light" flashlights, you can drape it around your neck, and aim it just where you need the light to fall on your knitting. I used on of these for a in bed reading light for a couple of years, and it worked very well. I hope you enjoy your trip.
I have tried 2 different models of clip-on book lights and I havent found them bright enough, but additionally, the width of the beam they provide is too narrow. I LIKE the idea of the snake light around your neck!