Finally took a chance on one of those cheap eBay 486 boards from Ukraine. It showed up after about a month exactly as advertised! Listing said it sometimes boots and sometimes doesn't,
The 486 Restoration – Part 1 – vswitchzero
foone🏳️⚧️ on Twitter: "The Socket 3 used by the 486 only provided 5v power, but the later Pentiums used in the Pentium Overdrive chips had switched to 3.3v." / Twitter