I've been using Mitsubishi Uni Nano Dia 0.7mm HB lead for years, but it appears it's been discontinued with no clear replacement. Its supposed replacement is Mitsubishi Uni "Smudge-Proof", but appears to only be available in 0.5mm. There is still some stock of *colored* Nano Dia in the correct size. Reddit suggestions: - [Pilot Neox](https://www.jetpens.com/Pilot-Neox-High-Purity-Graphite-Pencil-Lead-0.7-mm-HB/pd/6575) - [Pentel Ain Stein](https://www.amazon.com/gp/product/B00N98YK8I/ref=ewc_pr_img_3?smid=A3IMVM17EAURSO&psc=1)