OK, I said I would follow up when my key fob adventure came to an end, so here it is.
I got my second fob today. Unfortunately, due to not getting any responses from anyone about which fob model # to get, the one I got from eBay seems to have been the wrong one for my 2017, so I had to bite the bullet and buy the fob from the dealer. However, the dealer took pity on me and sold it to me for only like a 100% markup over the prices I see online for the fob, because I just couldn't not have a fob for my wife anymore. (Correct P/N was 95440-B2AC0 for my 2017 27kWh model, BTW. The one I got from eBay was 95440-E4000 -- I'd be happy to sell it for a good price to anyone here if they find that's the correct one for them. Something I saw online seems to indicate they may be interchangeable? The dealer said they could try to program it to the car, but if it failed, they'd charge me for the labor anyway, so I wasn't going to take that risk.)
Anyway, all told, I ended up paying around US$400 (not including the fob I bought from eBay) for the fob, the key cutting and the programming. Took about 90 minutes (was supposed to just take an hour, but apparently GDI crashed while trying to program it the first time, so they had to start over again).
The dealer didn't have any problem cutting an aftermarket key that goes into the fob, so it seems wise to bring one along, because they wanted something like $40 for the key, and you can get them on eBay for well under $10. Key P/N is 81996-A2010 (this is definitely correct, regardless of year for gen 1 Soul EV). The aftermarket one I got was from a seller called SF Fobs -- the key was shorter than the OEM one, but the OEM key sticks out of the Soul by inches, so it was no big deal. Fits perfectly into the OEM fob.
Anyway, my wallet is significantly lighter as a result of this mess, but at least I got a refund for the aftermarket one I tried to get from Ace Hardware, so that's something. Hope you all have a smoother experience than I did.
2017 Soul EV (base, silver)
Formerly owned 2012 Nissan Leaf SL