Hot Linguist Boyfriend just plugs a mic into his laptop and records away, straight into CoolEdit 2000 (abandonware now?).
He and the interviewee take a break occasionally so
he can hit Save now and then,
and maybe start a new file.
A few years ago, we got
of these Sony Voice Recorders.
Of course, "Sony" equals cursed.
The thing is an interface nightmare at every conceivable
level, including just getting the files ouf of it.
The only concession it makes to our non-Sony universe is that the mic and headphone jacks are standard 1/8", and the batteries are two AAAs. Because I would not put it past Sony to invent their own weird plug for even those things, and a triangular-shaped battery.
Good point: it's only 4" long, 1½" wide, and about a half inch thick.
But that means that there's barely a surface on the thing that doesn't have a very very complicated button or switch on it.
If you need something as small as this, this Sony thing is your choice of last resort.