Those Motacc bar ends will fit once the R3s weights are removed, but you shouldn't need them. The bar end mirrors will take the place of the stock bar ends.
The weights inside the bars can be removed by using a small flat blade screwdriver, or two, to pry the tabs up out of the slots they fit in. Weights will then slide right out.
Then just go back to using the bar ends as they came and the sliding pieces on them will tighten them right up.
If you notice vibration with the weights removed you can always coat them liberally with epoxy (or wrap them with electrical tape so they are a tight fit into the bars) and push them farther into the bars. If you use epoxy, make sure you clean out the end of the hole well after inserting the weights (and before the epoxy sets up), so that the bar ends will still fit and NOT get epoxied in!