Are there published testimonies from ex cessationists who became continuationists after personally witnessing or experiencing a sign gift? Has ever a cessationist Christian become a continuationist for first-hand experiential reasons? Are there published testimonies from ex cessationists who became continuationists after they had a first-hand experience with a sign gift or witnessed someone else exercising a sign gift?
If possible, I'd be especially interested in reading testimonies published by reputable former cessationists, say, a renowned cessationist Baptist pastor who had an experience that turned him into a continuationist, etc.

The counterpart question to this one can be found here.
Jack Deere has at least two books which relate to your question.  He was a professor at Dallas Theological Seminary, which is a cessationist seminary.
Some of his books which deal with the question are Why I am Still Surprised by the Power of the Spirit:Discovering How God Speaks and Heals Today and Surprised by the Voice of God:How God Speaks Today Through Prophecies, Dreams and Visions.  He wrote multiple other books on related topics.
He includes Biblical support and his own experience of conversion to speaking in tongues.
He includes personal experiences of reasons for his conversion to continuationist.  One example from the first edition is ongoing challenges with a specific student.  God prompts Jack to ask about pornography.  Normally, in that seminary, at the time this would be considered an extremely inappropriate question, even risking censure from the seminary.  However, the student confesses looking at pornography and that this was contributing to academic problems.  This was the beginning of the student getting free of sin with pornography.
https://wellspringdfw.libsyn.com/speaking-in-tongues-part-2-jack-deere  His sermon here speaks to the topic in general.
Also, Dennis Bennett, an Episcopal priest describes his journey from cessationist to continuationist in his book, Nine O'Clock in the Morning.  Although it was written in the 1970's, he describes many experiences of congregants converting from cessationist to speaking in tongues.  Many of them based their decisions or desire on seeing the joy, freedom or healing in friends who spoke in tongues.  He mentions other evidences which meet the biblical criteria, &quot;You will know them by their fruits&quot; from  https://www.biblegateway.com/passage/?search=Matthew%207%3A15-20&amp;version=NKJV
https://www.amazon.com/Nine-OClock-Morning-Episcopal-Discovers-ebook/dp/B08HKGFNSH
Bennett's book focuses more on the topic of baptism in the spirit, but clearly addresses the cessationist question.
Both of these books were instrumental in my personal conversion from from cessationist to speaking in tongues.