Bummer. Do you use that switch while playing? If not, you could probably get it into the position you prefer using a small screwdriver and leave it there while waiting for a replacement. I think having Alembic send you one might be quickest because although they're still being manufactured there are so many specific variations available in those small toggle switches that exactly what you're looking for is rarely stocked by distributors. But I'm sure there's a whole drawer of them at the Alembic HQ.
These things happen. It's all serviceable.
Oh, be sure to check your Entwistle kit of spares!
Jimmy J