I'm looking to find clients who are willing to pay a premium above usual contractor rates, for software that is developed with advanced tools and techniques to eliminate certain classes of bugs. However, I have little experience of contracting, and relatively few contacts.

It's important to state that the kind of tools and techniques I'm thinking of (e.g. formal verification) are used commercially extremely rarely, as far as I'm aware. There is kind of a continuum of approaches to higher reliability, with basic testing and basic static typing at one end and full-blown formal verification at the other, but the methods I'm thinking of are towards the latter end of the spectrum.