reading the question and replies makes me see a variety of interpretations of the question:
1. the technique demonstrated is a version of kote kaeshi that relies on proper timing to reach uke's hand while extended (i will assume that the asker was NOT grabbing for the hand but using what i think most teach, the contact the upper arm and slide down technique) and could not execute it in time. the cause of the problem: uke is striking too quickly, the solution: ask him to slow down.
i dislike the pat answer of 'just do another technique (than the one shown) or 'just hit him' to an uke that is not giving an attack appropriate to the technique demonstrated---why not just pull out a gun and shoot him then? nage would like to practice the technique just demonstrated.
2. asker wanted to know other techniques to do instead of what his instructor showed: answer: any of the above suggestions, or think up your own based on where you both are standing, etc...perhaps a kaiten nage since uke is probably resisting forward motion of his arm/fist by this point, or a sudori sankyo....