Some rummaging produced a tiny DPDT switch that actually fit the holes intended for a pin header on the recently arrived Ham It Up board, at least after I amputated 2/3 of the poor thing’s legs:

The new SMA noise output jack sits in the front left, with the white “noise on” LED just left of the switch:

There’s no way to measure these things accurately, at least as far as I can tell, but the holes came out pretty close to where they should be. The new SMA connector lined up horizontally with the existing IF output jack and vertically with the measured / rounded-to-the-nearest-millimeter on-center distance:

The Enable switch doesn’t quite line up with the LED, so the holes will always look like I screwed up:

That’s OK, nobody will ever notice.
Now, to stack up enough adapters to get from the SMA on the Ham It Up board to the N connector on the spectrum analyzer …