Your profile doesn't show where you are from Kim but I was able to purchase my system 4 through Dave at Anderwerks in Calgary Alberta. 1-403-277-4269 (he regularily travels to Germany).
I looked through my brochures but there are no part #s listed and the whole thing is in German.
My conversion kit consists of 2 plastic side panels that cover the mechanism on the side of the helmet. They snap into place and didn't "stay" well. Soooo----I JB Welded them on as I find the helmet far better for my needs as a 3/4.