We're out of stock but you can still order sets from https://newtonestrings.com/shop/jon-gomm-signature-master-class-strings/

Unique 14-68 gauge roundcore phosphor-bronze strings, for steel string acoustic guitars. Handmade in England by Newtone Strings, specially designed for the low tunings Jon uses, with a rich warm tone and lingering sustain. Learn more about them at https://jongomm.com/strings