well any loud noise will work, but it will also get him to start looking for what made it, 70 yrds is a long poke, if you were looking to stop for a shot

but I have over the yrs carried some rocks with me, more ot get deer out of a plot so I can climb down, but sure a rock tossed at him would get him to both stop and look in a different direction, and thus maybe allow you to the grunt, bleat or?? to get him closer to you for a shot?
a branch would work well too I think, or maybe even drop a day pack or likes
just bneed to bear there focus
but be careful too loud and it could make them run instead of stop!!