I looked up 1ss106 equivalent and found that NTE584 is supposed to be such: http://www.newark.com/nte-electronics/nte584/schottky-rectifier-35ma-20v-do/dp/31C5017?ost=NTE584&selectedCategoryId=&categoryId=800000055001&searchView=table&iscrfnonsku=false
Thanks Michael. They were very specific that only a Hitachi would work(not sure why) but I will give it a try.
Maybe contact the authors of the guide you are following? They might have special knowledge of where to get the component.