While We're Repairing Things: Replacement Pilot Down Force Clip
Here is a Very Specific Object. For one of the nine people in the world who own a Pilot Down Force pen (I already excluded myself from the total), here's a direct fit replacement clip for when yours breaks.
Who cares, and why? Well, part of this pen's deal is that the clip is absolutely required to use it. That's because the angled rib on the clip is part of the hold-open mechanism. No clip, no write.
It's twofold. That's half of it. The other half is there's a piston in the clicker button that pressurizes air against the ink in the cartridge so it'll do all the usual writes-upside-down-in-space-underwater malarkey. Only without the need for specialized pressurized cartridge.
Having the hold-open on the clip, separated from the pressurizer, probably immensely simplifies the mechanical design. And probably ironically makes it stronger.
In addition to not being cheap, it’s also not disposable. Pilot manufactures and sells refill cartridges - you can get them in office supply stores, on Amazon, at Walmart, and at dedicated pen retailers. And it took me all of two seconds to discover that with a simple web search.