Hi Ginny,
Unfortunately, I've been unable to track down any sermons or addresses online. I've found a handful of quotes and/or anecdotes which I'll link to at the end, but nothing that fits what you're looking for. I spoke with my father and he suggested emailing 1rst Presbyterian Church of Pittsburgh. They may have some archives. I'm sorry I can't be of more help, but please let us know if you find more than I did.
Andrew
Bruce Thielman online citations: