Where is the fuel injector relay located on a 1997 Oldsmobile Bravada?

You mean the fuel pump relay? I own a 97 Blazer, which is more the same as the Bravada, albeit 4WD vs. AWD, and I'm pretty sure the injectors themselves aren't electronic. For the pre-facelift Gen 2 Blazer, Jimmy, Bravada, and S10/S15, you open the glove compartment. In the back of it, you'll see a plastic cover which says "relay access". Remove that panel, and you can access your relays (minus the AC system relays, which are located elsewhere). Don't recall off the top of my head which one it is in there, but the diagram on the cover should tell you.

On the facelifted Gen 2 models (98 and up), there's another fuse/relay panel under the hood, and that's where that relay will be on those models. But I'm pretty sure Bravadas kept the same electrical system configuration as the rest of the vehicles on that platform prior to the facelift.