The Narrow-Grip Floor Press
While dips could work equally well at developing your triceps, these presses are far more useful for the average gym population since they don't beat up your shoulders as much.
The floor press limits shoulder range of motion while loading the portion of the press where your triceps are the most dominant. Unlike many dipping bars, you also have the choice of grip width, making them better aligned for your elbows too.
You could use a straight bar, thick bar, or even a football bar.