I found a lugged 750 for $40 on Craigslist a few years ago. It was not rideable as purchased but that was OK since I had most everything I needed to make it a drop bar commuter. The paint was rough in some places with a few rust spots so I just sanded them and shot the spots with black paint.
I first bought some Continental TourRide tires in 700c in 2015 and put 26" on the 750. With both 700c and 26" I have never had a flat. They are affordable as well, generally under $25 each.