It's certainly a significant problem, and one that would cause some intense short-term pain, AND one that we should just bite the trivial cost and make a spare

It's certainly a significant problem, and one that would cause some intense short-term pain, AND one that we should just bite the trivial cost and make a spare set somewhere for, but...... It would take years in normal times. In a crisis like this, you'd see resources allocated to transformers on the scale of (perhaps greater than) that allocated to COVID-19 vaccines and PPE, and that time scale would almost certainly be dramatically reduced.