SRS:
This year, Harris lost to Trump by only 780,000 votes in the swing states, compared to 3.2 million nationally under current vote counts. So it would have taken the VP flipping just under one million votes into those areas to be the president-elect today.

To overturn a margin of 780,000 votes doesn't need one million 'flips'. It's less than half that figure.
Each vote 'flipped' would reduce Trump's votes by 1, and increase Harris's by 1. so 390,001 'flips' would do the trick. (adjust to allow for weird voting systems)