Or you could get a different stem with a single bolt, or an internal wedge system like a syncros.
Or..........
I have in the past rigged up a system where I fit another starnut into a small piece of cut-off steerer tube and then run a long stem bolt down through the stem cap and both star nuts clamping the whole mess together - definitely an 'at-your-own-risk' fix, but I have raced with this set up and had no-problems.