I use one of these, scroll down till you get to "switchbone"

http://www.guitarandampshop.co.uk/acatalog/Radial_Pedals.html

Not cheap but very good

or there is..

http://www.piedog.com/musical_instruments/guitar/guitar_effects/electric_guitar_effects/boss-ls_2.htm


Don't know how good this one is. Over the years I've had some great kit form Boss however they have also made some real schlock !