How direct-bolt-in are you looking for? Everything is going to need some sort of modification to mount. Several guys have used seats from late model Ram or F150 trucks that have integrated shoulder belts. You have to be careful with those, though, as lots of them have the lockup part connected into the computer, so it takes some monkeying around with electrical to get them to work properly.
Myself, I'm trying to get my hands on a split folding bench out of a '70's club cab, so I can access the storage behind my seat (once I move the gas tank, that is). But then again my lower back likes the support old style bench seats provide...