The bog standard Dunlop Cry Baby (or one of its many variants) will do the job. Personally I think the design has a few disadvantages: firstly, you have to depress the pedal fully down to click the siwtch & turn it on, so the wah starts from the "top" of the sweep. Also, it's a bit top heavy - I've tipped them over when not glued to a pedal board before & they do get a bit crackly & wear out after a while...
But IMHO the Morley Bad Horsie is the best wah out there. For starters it's switchless - the pedal is spring loaded in the "back" position. You simply move it off the bottom & the wah turns on, take your foot off it & it goes back & turns off. Also, it's whisper quiet, Morley typically put a wider, deeper sweep on them & they are built like tanks! :)