The Staedtler lead holder is a perfect BIFL product. I had mine for years until I somehow lost it. I couldn't find a Staedtler at a store near me, so I ended up buying one from a brand called Alvin. I hadn't heard of it before, but it feels like it'll also last forever. Has a metal body and everything. https://alvindrafting.com/products/pro-matic-metal-lead-holder
Other upside of a lead holder: no more little broken 0.5 mm pieces ending up all over the room.