This is what I use:

http://www.specialtyarch.com/hoodedballpeep.htm

Scroll down to the bottom of that page and you will see a "NEW" logo for the 1/4 inch hooded super ball peep for hunters in low light conditions. That's the one I'm using. If you think 1/4 is too big then you can always install one of their inserts to make the hole whatever size you wish.