This is a very simple creation that anyone can do, but you do need a few non-standard parts. First is the white 1x1 slope - this currently comes in the ARC-170 and in some of the newer X-pods. Next, a half-pin - ideally, it should be white, but grey doesn't look bad either.
Which R2 body is important - unfortunately, you will need one of the older types. Newer types now have a cross section in the middle so that an axle can fit in. The older pieces merely have a hollow tube inside.
Very good. for those of you who only have the new R2s there is a way that involves a little bit of cutting. all you need to do is cut a lightsaber handel in half, stick the part a minifig would hold in the R2, and attach the white slope to where the blade comes out. Like i said wery good 'purist' idea