you mean building kit for you to solder and put together a pedal or finished product from an effect building kit?
google for tymc or ty music center. They have a forum in here too and located at peninsular
They do bring in byoc(build your own clone) building kit, either ready made or sold as kit. You might like to check with them
if you refering to diy pedals where the info on schematic and layout are available easily over the net, most of it dont really sell building kit(theres some that give info as well as selling also though), those might need to hunt for components yourself, read the schem, do own layout(if no layout diagram available) and put everything together.