Thanks Jason!
I ran around to a few local retailers and realized pretty quickly that 8GB cards are, to use the vernacular of the cool kids, unobtanium. Not much available at retail locations smaller than 128GB. (Amazon has 8GB cards in stock, but even with Prime, they're a week away.) (yeah, first world problems)
An 8GB card was located in one of my other devices and after reformatting to the specified params, it worked!
As an aside: after looking inside while I was retrieving a mis-aimed SD card, I noticed that the SD card connector won't allow the card to be inserted all the way in. There will still be a bit of the card poking out the back. Glad I didn't force it.
Bottom line: 2GB cards are too small, 32GB cards are too big. 8GB is just right.