I have been looking at doing this myself, I think the bonnet badge is 70mm, smaller than the standard BMW size on all the other models. Had a look on eBay and all complete badge sets don't have that size, so I think a bit of modification is required.
The 70mm black badges from Ian Clifton are standard badges with a black/white 65mm sticker stuck to it. I'd advise saving the £20 he charges, buy a 65mm flat sticker from EBay and do it yourself.