IMO the fastest 559 tyre is the Conti GP but as you say, it’s only available in 28mm width (and actually comes up a bit narrower than that on my rims). I’ve also found 559x40 Vittoria Rubino Pro’s to roll well but it sounds like that’s too big for you and they’re also no longer made
The Conti Sport Contact is available in 32mm width I think but, from my experience with the 700c version, is a bit sluggish.
Could you substitute a 650b wheel instead of 700c? There a few fast tyres in that size including the Conti GP5000.