Left Luggage at Pisa Field of Miracles

I would think a Complete Visit qualifies
Lots of people skip the Tower climb

No experience myself

Two years ago, we visited at the Field of Miracles (no Tower climb for us, either, but be sure to include the Camposanto Monumentale in your visit. It’s the building to your right as you face the entrance to the Baptistry or to your left as you face the entrance to the Cathedral. The surviving frescoes are stunning.

We arrived, and were continuing onward by train, so we did come and go from the Stazione Centrale. The shuttle between Centrale and the Field of Miracles was cheap and quick, and offered an interesting view of more of the city. Although this doesn’t fit with your intentions, I just wanted to confirm that there was a baggage check at Centrale, on the far left side of the station from the entrance, beyond the cafe. I don’t remember the cost, but they charged for every single piece of luggage, not per group, and the line took almost forever for the one guy at the counter to slowwwwwly wait on people. My husband had a smallish daypack at the sights, but I suspect it was smaller than the carry-on pack you’re describing.

I can’t say whether your bag would be welcomed at the Baptistry, Camposanto, and Cathedral, but could maybe carrying it in your arms make a difference? I hope you find an acceptable way to manage your luggage while there. They will definitely let you know your options once you’re there.

The Bounce app has luggage storage options nearby.