I'm missing one of mine as well.... I've mulled over several ways forward,
several of which you've already considered. It looks to me as if the originals were die cast aluminum.
* sand casting. This could be made to work (the remaining one could be used as a loose pattern), but I doubt I could manage to cut down the porosity enough to look good; I'd have to farm this out. There would be shrinkage, but since it's hard to see both badges at the same time when installed, this prob. doesn't matter too much. Getting real clean detail at the bottom of the script is going to be hard.
* cast in aluminum filled epoxy into a female urethane mold made from remaining badge. Straightforward , can be done at home... unlikely to be very shiny, though.
* Convince Webspinner (Barbie) to take the CNC course at Tech-Shop and use the CNC mill to make several. Time consuming, since small radius detail on script forces use of a small cutter which will take a while since machine is likely RPM limited.