Thanks for asking such a great question. We seem to get a lot of questions for people looking for topic-specific surveys. One place that I find invaluable is Google Scholar (http://scholar.google.com/). It does not have the usual filters for journal quality that you might find with the National Library of Medicine (MedLine, PubMed), but you will find a lot of related journal articles that reference the survey of your choice. I did a quick search using the terms "self-efficacy" and "youth", and the search engine returned about 15,000 references. The first 10 were all quite relevant to your question, so I am sure that you could quickly find an article, and contact the authors to see if they can provide the instrument they used. We do hope this helps you in your search.
