Hey there,
is there a replacement for the LMC567 IC in the thing modulator?
http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html
No. AFAIK, there is only one LMC567, made by National Semiconductor. The easiest source to obtain one is Digikey. Be sure to specify the 8 pin DIP version, unless you want surface mount.