You could make a bookmarklet that injects that CSS when you click on it and then leave it in the bookmarks bar. There used to be a couple of these that were go

You could make a bookmarklet that injects that CSS when you click on it and then leave it in the bookmarks bar. There used to be a couple of these that were good, Clear Read and Readable were the two I remember, but they all seem to have stopped working over time.