You can try the usual places but I doubt such a thing exists.

It can't be done, at least with any integrity to the battle in hand. Infinity Engine saves simply do not include that kind of detail in the data. At best you would be dumped back in the same spot for the game to start battle again.

Yeah, it looks like the Infinity Engine's saving paradigm is actually fairly shoestring in certain ways (in direct contrast to, say, the Aurora Engine - you can save in battle to your heart's content in Neverwinter Nights or KotOR, and there's a couple fights that are hard enough that this can actually be seriously handy).

Case in point, the fact that even an animated AoE spell effect is enough to shut down your ability to save (quite a pain really, especially in Icewind Dale! ...) - even if there's no combat going on or other reason you shouldn't be able to save! Just "YOU CANNOT SAVE AT THIS TIME" (and voiced at you in the BG games' case :P).

There has to be a reason that's the case (although on the other hand, you can still leave the area, even if it's an Auto-Save area transition; perhaps reloading such an autosave and seeing what goes wrong if anything would indicate why this is enforced?).