Where may these written testimonies be found?
Um, in the Bible. To be specific, the New Testament; all of it.
Here are some links to the text in the original language:
http://biblestudytools.net/InterlinearBible/
http://www-users.cs.york.ac.uk/~fisher/gnt/
http://www.ntgateway.com/greek/
What peer review exists for these written testimonies?
Within the books of the NT, the writers often refer to what other writers have written. IF that were false, they would have stated so.
Luke 1:1-4 Inasmuch as many have undertaken to compile an account of the things accomplished among us, just as they were handed down to us by those who from the beginning were eyewitnesses and servants of the word, it seemed fitting for me as well, having investigated everything carefully from the beginning, to write it out for you in consecutive order, most excellent Theophilus; so that you may know the exact truth about the things you have been taught.
I John 1:1-3 What was from the beginning, what we have heard, what we have seen with our eyes, what we have looked at and touched with our hands, concerning the Word of Life -- and the life was manifested, and we have seen and testify and proclaim to you the eternal life, which was with the Father and was manifested to us -- what we have seen and heard we proclaim to you also, so that you too may have fellowship with us; and indeed our fellowship is with the Father, and with His Son Jesus Christ.
How can the events described in these testimonies be reproduced for independent observation by others?
Simple, anybody can do it (run the experiment , if you will); it's just a matter of repenting and trusting Christ for salvation. When that happens, a person is spiritually reborn. It happens every time. There are millions of people whose lives are changed as a result of this. They consistently give the same account. It can be observed internally by the person doing it and externally by seeing the change in the lives of the people who have done it. It's been well documented over thousands of years and there are people on this forum right now who can give testmony to that very thing happening in not only their lives but hte lives of their family and friends.